High yield imaging, chest 9781416061618, 1416061614

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HIGH-YIELD IMAGING: CHEST

ISBN: 978-1-4160-6161-8

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Part 1 

CONSOLIDATION

Focal Consolidation: Acute Causes DEFINITION: Focal consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material at a single pulmonary focus. IMAGING

DIAGNOSTIC PEARLS

Radiography

n N  onsegmental

Findings

homogeneous opacity that is associated with obscuration of the pulmonary vessels and little or no volume loss. n A  djacent soft tissue structures are obscured: silhouette sign. n M  argins are poorly defined except where the consolidation abuts the pleura. n A  ir-containing bronchi (air bronchograms) are frequently visible within areas of consolidation. n N  onsegmental (lobar) pneumonia may be associated with increased volume and bulging of the interlobar fissure. n S  egmental consolidation may be seen in pneumonia, distal to bronchial obstruction, and in association with acute pulmonary embolism. n S  pherical (round) areas of consolidation may occur in pneumonia or occasionally in pulmonary hemorrhage. n L  ung contusion results in focal consolidation that crosses normal anatomic boundaries. n F  ocal right upper lobe pulmonary edema typically occurs secondary to papillary muscle dysfunction after acute myocardial infarction. n F  airly

Utility

sign is most useful in differentiation of middle lobe and lingular disease from lower lobe disease and may also provide precise anatomic information in other sites. n R  adiography is usually the first and often the only imaging modality used in the assessment of focal consolidation. n S  ilhouette

CT

Findings

homogeneous increase in pulmonary parenchymal attenuation that obscures the margins of vessels and airway walls. n G  round-glass opacities indicating incomplete filling of alveoli adjacent to airspace consolidation. n C  onsolidation:

consolidation is associated with air bronchograms and normal or increased lung volume. n S  egmental consolidation is typically associated with atelectasis and lack of air bronchograms. n P  arenchymal consolidation may result in poorly defined 5- to 10-mm nodular opacities known as airspace nodules.

Utility

to radiography in demonstrating presence of focal consolidation or ground-glass opacity and the presence of underlying lung disease.

n S  uperior

CLINICAL PRESENTATION n F  ever

and cough are present in patients with pneumonia. shortness of breath may occur in patients with pulmonary embolism. n S  ome patients may be asymptomatic or present with nonspecific symptoms. n A  cute

DIFFERENTIAL DIAGNOSIS n B  acterial,

viral, or fungal pneumonia pneumonia n A  cute pulmonary embolism n P  ulmonary hemorrhage n A  spiration

PATHOLOGY of gas within the airspaces by fluid, blood, or other material.

n R  eplacement

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY causes of acute focal consolidation include pneumonia (bacterial, viral, fungal), hemorrhage, and pulmonary edema.

n C  ommon

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW of silhouette sign is only reliable on radiographs performed using proper technique. should be considered particularly in patients with hemoptysis and those with blunt chest trauma. n F  ocal opacities are more commonly seen on high-resolution CT than on radiography. n A  ssessment

n H  emorrhage

2

CONSOLIDATION

Figure 1.  Parenchymal consolidation and silhouette sign. Posteroanterior chest radiograph shows consolidation in the right lower lung zone. Note obscuration of the right-sided heart border (silhouette sign) consistent with consolidation in the right middle lobe. The dome of the right hemidiaphragm is clearly seen consistent with sparing of the basal segments of the lower lobes. The patient was a 37-year-old man with right middle lobe pneumonia.

Figure 3.  Round pneumonia. Posteroanterior chest radiograph shows round mass-like area of consolidation (arrow) in the right middle lobe. The patient was a 41-year-old man who presented with fever and cough. Incidental note is made of azygos fissure.

n S  egmental

consolidation with or without volume loss typically results from endobronchial obstruction or pulmonary infarction. n S  egmental distribution seen after aspiration and with pneumonia caused by Staphylococcus aureus, Streptococcus pyogenes, or a variety of gram-negative bacteria. n R  ound pneumonia occurs much more frequently in children than in adults. n A  lthough round pneumonia in adults may result from bacterial infection, most commonly no organism is identified. n F  ocal right upper lobe pulmonary edema is seen most typically with myocardial infarction resulting in papillary muscle dysfunction or rupture and acute mitral regurgitation.

Focal Consolidation: Acute Causes    3

Figure 2.  Bulging fissure sign. Anteroposterior chest radiograph shows dense right upper lobe consolidation with increase in volume of the right upper lobe and inferior bulging of the minor fissure (arrows). The patient was a 64-year-old man with Streptococcus. pneumoniae pneumonia.

Figure 4.  Right upper lobe pulmonary edema due to acute mitral regurgitation. Anteroposterior chest radiograph shows prominence and ill-definition of the pulmonary vascular markings and septal lines consistent with interstitial pulmonary edema. Also noted is extensive right upper lobe consolidation. Although the upper lobe consolidation is most suggestive of a pneumonia, it was proved to be due to airspace pulmonary edema secondary to acute mitral regurgitation after myocardial infarction. The patient was an 83-year-old woman.

Suggested Readings Gluecker T, Capasso P, Schnyder P, et al: Clinical and radiologic features of pulmonary edema. RadioGraphics 19:1507-1531, 1999. Grenon H, Bilodeau S: Pulmonary edema of the right upper lobe associated with acute mitral regurgitation. Can Assoc Radiol J 45:97-100, 1994. Wagner AL, Szabunio M, Hazlett KS, Wagner SG: Radiologic manifestations of round pneumonia in adults. AJR Am J Roentgenol 170:723-726, 1998.

Focal Consolidation: Chronic Causes DEFINITION: Focal consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material at a single pulmonary focus.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n F  ocal

Findings n F  airly

homogeneous opacity associated with obscuration of the pulmonary vessels and adjacent soft tissue structures is known as a silhouette sign. n A  ir-containing bronchi (air bronchograms) are frequently visible within areas of consolidation. n C  onsolidation in pulmonary carcinoma and lymphoma may be round or have irregular margins. n C  hronic segmental or lobar consolidation with or without associated volume loss suggests bronchial obstruction by tumor or foreign body. n C  hronic focal nonsegmental consolidation often with irregular and poorly defined margins may be seen in lipoid pneumonia. Utility

n S  ilhouette

sign is most useful in differentiation of middle lobe and lingular disease from lower lobe disease and it may also provide precise anatomic information in other sites. n C  hest radiograph is useful in demonstrating the presence of focal consolidation and in monitoring changes over time.

CT

Findings

n C  onsolidation

is a homogeneous increase in pulmonary parenchymal attenuation that obscures the margins of vessels and airway walls. n G  round-glass opacity is a homogeneous increase in attenuation that does not obscure underlying vessels. n A  small, round, focal ground-glass opacity is a common manifestation of bronchioloalveolar cell ­carcinoma. n T  he presence of a solid component in association with the focal ground-glass opacity is suggestive of adenocarcinoma. n C  hronic focal area of consolidation with air bronchograms may represent a carcinoma or primary pulmonary lymphoma (maltoma). n F  ocal consolidation with localized areas of fat density (−30 to −120 Hounsfield units) is virtually diagnostic of extrinsic lipoid pneumonia.

consolidation progressing slowly over several months is suggestive of bronchioloalveolar carcinoma or lymphoma. n P  ulmonary lymphoma may result in single or ­multiple mass-like areas of consolidation. n P  resence of fat attenuation in focal consolidation is characteristic of lipoid pneumonia.

Utility

n S  uperior

to radiography in the differential diagnosis. to radiography in demonstrating presence of bronchial obstruction. n F  requently allows diagnosis of lipoid pneumonia by demonstrating areas of fat density. n S  uperior

CLINICAL PRESENTATION n F  ocal

ground-glass opacity or consolidation is frequently an incidental finding in asymptomatic patients. n S  ymptoms when present are nonspecific, usually consisting mainly of cough and, occasionally, shortness of breath and hemoptysis.

DIFFERENTIAL DIAGNOSIS n O  rganizing

pneumonia pneumonia n P  ulmonary Hodgkin lymphoma n P  ulmonary non-Hodgkin lymphoma n B  ronchioloalveolar cell carcinoma n A  denocarcinoma n L  ipoid

PATHOLOGY n R  eplacement

of gas within the airspaces by fluid, protein, cells, or other material n B  ronchial obstruction with distal obstructive pneumonitis and atelectasis in endobronchial lesions

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n P  ulmonary

carcinoma should be suspected in patients with ground-glass opacities or consolidation that is progressive over several months. n C  hronic segmental consolidation with or without atelectasis should suggest the presence of an ­endobronchial lesion with distal obstruction. n C  T commonly allows the diagnosis of lipoid pneumonia by demonstrating the presence of fat within the consolidation.

4

CONSOLIDATION

Figure 1.  Primary pulmonary lymphoma. Posteroanterior chest radiograph shows focal consolidation in the right lower lung zone (arrow). Note focal obliteration of the right-sided heart border (silhouette sign) at the level of the consolidation. The patient was a 53-year-old man with primary lymphocytic lymphoma of the lung (maltoma).

Figure 3.  Primary pulmonary lymphoma. CT image shows focal con­­ solidation (arrow) in the right middle lobe. The patient was a 53-yearold man with primary lymphocytic lymphoma of the lung (maltoma).

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n S  egmental

consolidation with or without volume loss typically results from endobronchial obstruction or pulmonary infarction. n C  hronic lobar consolidation and atelectasis are usually due to an endobronchial tumor. n L  ipoid pneumonia results from aspiration of mineral, vegetable, or animal oil. n I n approximately 80% of patients with lipoid ­pneumonia, focal areas of fat attenuation can be seen on CT.

Focal Consolidation: Chronic Causes    5

Figure 2.  Lipoid pneumonia. Posteroanterior chest radiograph shows focal consolidation in the right upper lobe. The patient was a 55-year-old man with lipoid pneumonia confirmed by fineneedle biopsy and clinical history.

Figure 4.  Lipoid pneumonia. High-resolution CT image demon­ strates small foci of fat attenuation (arrows) within the parenchymal consolidation. The patient was a 55-year-old man with lipoid pneumonia confirmed by fine-needle biopsy and clinical history.

Suggested Readings King LJ, Padley SP, Wotherspoon AC, et al: Pulmonary MALT lymphoma: Imaging findings in 24 cases. Eur Radiol 10:1932-1938, 2000. Lee KS, Kim Y, Han J, et al: Bronchioloalveolar carcinoma: Clinical, histopathologic, and radiologic findings. RadioGraphics 17:13451357, 1997. Lee KS, Müller NL, Hale V, et al: Lipoid pneumonia: CT findings. J Comput Assist Tomogr 19:48-51, 1995. Raz DJ, Kim JY, Jablons DM: Diagnosis and treatment of bronchioloalveolar carcinoma. Curr Opin Pulm Med 13:290-296, 2007. Travis WD, Garg K, Franklin WA, et al: Bronchioloalveolar carcinoma and lung adenocarcinoma: The clinical importance and research relevance of the 2004 World Health Organization pathologic criteria. J Thorac Oncol 1(9 Suppl):S13-S19, 2006.

Multifocal Consolidation: Acute Causes DEFINITION: Multifocal consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material in two or more areas of the lungs.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  ronchopneumonia

Findings

n M  ultifocal

areas of consolidation presenting acutely are commonly ill defined but may become rapidly ­confluent. n A  ir bronchogram may be associated. n B  ronchopneumonia (bacterial, fungal, or viral) typically results in patchy unilateral or bilateral asymmetric consolidation that may have lobular, subsegmental, or segmental distribution. n P  oorly defined fluffy 5- to 10-mm nodules (airspace nodules) may be evident on the radiograph. n D  iffuse pulmonary hemorrhage (e.g., Goodpasture syndrome, microscopic polyangiitis, Wegener granulomatosis) most commonly results in symmetric, bilateral, poorly defined areas of consolidation. n H  ydrostatic pulmonary edema tends to involve mainly the central lung regions and is commonly associated with septal (Kerley B) lines. Utility

n U  sually

the first imaging modality performed in the evaluation of patients with suspected acute airspace disease. n H  elpful in detecting the presence of consolidation and in monitoring disease progression.

CT

Findings

n B  ronchopneumonia

is characterized by multifocal lobular or confluent areas of consolidation, centrilobular nodules, and branching linear opacities (“tree-in-bud” pattern). n G  round-glass opacities denote incomplete filling of alveoli adjacent to airspace consolidation. n D  iffuse pulmonary hemorrhage most commonly results in symmetric bilateral ground-glass opacities or poorly defined areas of consolidation that often have a lobular distribution. Utility

n S  uperior

to chest radiography in demonstrating presence and extent of disease, presence of underlying lung disease, and presence of complications.

CLINICAL PRESENTATION n A  cute

multifocal consolidation usually results in cough and shortness of breath.

is characterized by multifocal lobular areas of consolidation, centrilobular ­nodules, and tree-in-bud pattern. n P  ulmonary edema and diffuse pulmonary ­hemorrhage tend to be bilateral and symmetric and to have a central predominance.

n F  ever

is usually present in bronchopneumonia. occurs in patients with diffuse pulmonary hemorrhage.

n H  emoptysis

DIFFERENTIAL DIAGNOSIS n A  spiration

pneumonia

n B  ronchopneumonia n H  emorrhage

PATHOLOGY n R  eplacement

of gas within the airspaces by fluid, protein, cells, or other material. n I nflammatory exudate in bronchopneumonia. n D  iffuse pulmonary hemorrhage in patients with vasculitis (e.g., Goodpasture syndrome, microscopic polyangiitis, Wegener granulomatosis).

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  auses

of acute multifocal consolidation are bronchopneumonia (bacterial, viral, fungal), hemorrhage, and pulmonary edema.

Suggested Readings Gluecker T, Capasso P, Schnyder P, et al: Clinical and radiologic features of pulmonary edema. RadioGraphics 19:1507-1531, 1999. Herold CJ, Sailer JG: Community-acquired and nosocomial pneumonia. Eur Radiol 14(Suppl 3):E2-20, 2004 Mar. Hiorns MP, Screaton NJ, Muller NL: Acute lung disease in the immunocompromised host. Radiol Clin North Am 39:1137-1151, 2001:vi. Kjeldsberg KM, Oh K, Murray KA, Cannon G: Radiographic approach to multifocal consolidation. Semin Ultrasound CT MR 23:288-301, 2002.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n H  emorrhage

should be considered particularly in patients with hemoptysis and in patients with blunt chest trauma. n N  odular opacities are more commonly seen on high-resolution CT than on radiography.

6

CONSOLIDATION

Figure 1.  Multifocal consolidation in bronchopneumonia. Posteroanterior chest radiograph shows patchy consolidation in the left upper and lower lobes. Note inhomogeneous increased opacity of the left heart compared with the region of the right atrium consistent with consolidation in the retrocardiac region of the left lower lobe.

Figure 3.  Multifocal consolidation in diffuse pulmonary hemorrhage. Posteroanterior chest radiograph shows dense consolidation in the right upper lobe and poorly defined areas of consolidation and ground-glass opacities in the lower lung zones.

Multifocal Consolidation: Acute Causes    7

Figure 2.  Airspace nodules. Magnified view of the left upper lobe in a patient with bronchopneumonia shows several round opacities with poorly defined margins. These represent airspace nodules and have been shown histologically to reflect the presence of peribronchiolar (centrilobular) consolidation.

Figure 4.  Bronchopneumonia due to Streptococcus pneumoniae. Coronal reformatted CT image demonstrates centrilobular nodular opacities and small foci of consolidation in the right upper and middle lobes and, to lesser extent, left upper lobe. The patient was a 29-year-old man with acute myelogenous leukemia and S. pneumoniae pneumonia.

Multifocal Consolidation: Chronic Causes DEFINITION: Multifocal consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material in two or more areas of the lungs. IMAGING

DIAGNOSTIC PEARLS

Radiography

n O  rganizing

Findings

n A  ir-containing

bronchi (air bronchograms) are frequently visible within areas of consolidation. n O  rganizing pneumonia most frequently presents as patchy nonsegmental unilateral or bilateral areas of consolidation. n C  hronic eosinophilic pneumonia typically has homogeneous consolidation involving mainly peripheral lung regions of middle and upper lung zones. n S  arcoidosis may result in peribronchial or, less commonly, peripheral areas of consolidation. n M  ultifocal consolidation may be seen in pulmonary lymphoma. Utility

n U  sually

the first imaging modality used in the evaluation of patients with suspected consolidation. n O  f limited value in the differential diagnosis of chronic multifocal consolidation.

CT

Findings

n M  ultifocal

consolidation typically associated with ground-glass opacities and small nodules is an uncommon manifestation of bronchioloalveolar carcinoma. n O  rganizing pneumonia most commonly results in bilateral consolidation that is often predominantly peribronchial or peripheral in distribution. n L  ess common findings include ground-glass opacities, centrilobular nodules, perilobular opacities, and reverse halo sign (focal area of ground-glass opacity surrounded by crescentic or ring-shaped consolidation). n C  hronic eosinophilic pneumonia appears as peripheral and predominantly upper lobe consolidation; similar findings may be seen in Churg-Strauss syndrome. n L  ocalized collections of fat in patients with consolidation are characteristic of lipoid pneumonia. n M  ultifocal consolidation may be seen in pulmonary lymphoma.

pneumonia (bronchiolitis obliterans organizing pneumonia) typically has a peribronchial and peripheral distribution. n C  hronic eosinophilic pneumonia typically has upper lobe predominance and peripheral distribution. n P  ulmonary lymphoma may result in single or ­multiple mass-like areas of consolidation.

Utility n C  T

is superior to radiography in the differential diagnosis of chronic multifocal consolidation. n P  resence of foci of fat density in areas of consolidation on CT is highly suggestive of lipoid pneumonia.

CLINICAL PRESENTATION n S  ome

patients may be asymptomatic or present with nonspecific symptoms. n P  atients with sarcoidosis typically have mild symptoms even in the presence of extensive bilateral consolidation. n P  atients with cryptogenic organizing pneumonia commonly present with cough, dyspnea, and low-grade fever. n T  he majority of patients with chronic eosinophilic pneumonia have peripheral eosinophilia, and approximately 50% have a history of asthma or atopy.

DIFFERENTIAL DIAGNOSIS n O  rganizing

pneumonia of known etiology pneumonia n P  ulmonary Hodgkin lymphoma n P  ulmonary non-Hodgkin lymphoma n C  hronic eosinophilic pneumonia n L  ung cancer: Bronchioloalveolar cell carcinoma n C  ryptogenic organizing pneumonia (idiopathic bronchiolitis obliterans organizing pneumonia) n L  ipoid

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n I n

the proper clinical context, the presence of bilateral areas of consolidation that are increasing in extent over several weeks in spite of antibiotics is suggestive of organizing pneumonia. n I n chronic eosinophilic pneumonia, the characteristic pattern of bilateral consolidation involving ­predominantly or exclusively the peripheral regions of the upper lobes is apparent on the chest radiograph in approximately 60% of patients and on CT in 85% to 100% of cases. n T  he diagnosis of lipoid pneumonia can be frequently made on CT by the presence of foci of fat density within the areas of consolidation.

8

CONSOLIDATION

Figure 1.  Cryptogenic organizing pneumonia. Posteroanterior chest radiograph shows patchy bilateral areas of consolidation and ground-glass opacities. The patient was a 50-year-old woman with cryptogenic organizing pneumonia.

Figure 3.  Cryptogenic organizing pneumonia. High-resolution CT image shows bilateral, peripheral, and peribronchial consolidation in the upper lobes. The patient was a 55-year-old woman with cryptogenic organizing pneumonia.

PATHOLOGY n G  as

within the airspaces is replaced by fluid, protein, cells, or other material. n O  rganizing pneumonia is characterized by presence of buds of loose granulation tissue within alveolar ducts and air spaces. n C  hronic eosinophilic pneumonia is characterized by filling of the alveolar airspaces by an inflammatory infiltrate containing a high proportion of eosinophils. n N  umerous lipid-laden macrophages, inflammatory cellular infiltration, and a variable amount of fibrosis in lipoid pneumonia.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  lthough

most cases of organizing pneumonia are idiopathic, similar reaction pattern may also be seen in many clinical settings.

Multifocal Consolidation: Chronic Causes    9

Figure 2.  Bronchioloalveolar carcinoma. High-resolution CT image shows extensive consolidation and mild volume loss in the right middle lobe and patchy consolidation, ground-glass opacities, and small nodular opacities in the lower lobes. The patient was a 71-year-old woman with bronchioloalveolar carcinoma.

Figure 4.  Chronic eosinophilic pneumonia. High-resolution CT image shows bilateral peripheral areas of consolidation. The patient was a 48-year-old woman with chronic eosinophilic pneumonia.

n L  ipoid

pneumonia results from aspiration of mineral, vegetable, or animal oil. n A  pproximately 50% of patients with chronic eosinophilic pneumonia have a history of asthma or atopy.

Suggested Readings Cordier JF: Cryptogenic organising pneumonia. Eur Respir J 28:422446, 2006. Jeong YJ, Kim KI, Seo IJ, et al: Eosinophilic lung diseases: A clinical, radiologic, and pathologic overview. RadioGraphics 27:617-637, 2007:discussion 637–639. King LJ, Padley SP, Wotherspoon AC, et al: Pulmonary MALT lymphoma: Imaging findings in 24 cases. Eur Radiol 10:1932-1938, 2000. Kjeldsberg KM, Oh K, Murray KA, Cannon G: Radiographic approach to multifocal consolidation. Semin Ultrasound CT MR 23:288-301, 2002.

Diffuse Consolidation: Acute Causes DEFINITION: Diffuse consolidation occurs after replacement of gas within the airspaces by fluid, protein, cells, or other material throughout most of the lungs. IMAGING

DIAGNOSTIC PEARLS

Radiography

n F  airly

Findings

n H  ydrostatic

pulmonary edema: consolidation in the perihilar regions (butterfly or bat wing distribution) associated with thickening of interlobular septa. n C  ommon ancillary findings: cardiomegaly and enlarged pulmonary vessels. n A  cute respiratory distress syndrome: initially patchy then becomes rapidly confluent and diffuse. n D  iffuse pulmonary hemorrhage: patchy or confluent bilateral areas of consolidation that tend to involve middle and lower lung zones. Utility

n U  sually

the first and frequently the only imaging modality used in the assessment of these patients. n L  imited value in the differential diagnosis.

CT

Findings

n H  ydrostatic

pulmonary edema tends to have perihilar and gravitational distribution. n A  ssociation is common with smooth interlobular septal thickening and small pleural effusions. n A  cute respiratory distress syndrome shows as bilateral consolidation and/or ground-glass opacities that may be patchy or diffuse. n S  eptal thickening and smooth intralobular lines are frequently superimposed on ground-glass opacities resulting in “crazy-paving” pattern. n R  adiologic manifestations of acute interstitial pneumonia are those of acute respiratory distress syndrome. n D  iffuse pulmonary hemorrhage shows as bilateral patchy or confluent areas of consolidation and/or ground-glass opacities; poorly defined centrilobular nodules may be seen.

homogeneous opacity associated with ­ bscuration of the pulmonary vessels and little or o no volume loss. n A  cute respiratory distress syndrome: initially patchy then becomes rapidly confluent and diffuse. n D  iffuse pulmonary hemorrhage: bilateral patchy or confluent areas of consolidation and/or ­ground-glass opacities.

DIFFERENTIAL DIAGNOSIS n S  evere

pneumonia edema n P  ulmonary hemorrhage n A  cute respiratory distress syndrome n A  cute interstitial pneumonia n P  ulmonary

PATHOLOGY n I nterstitial

and airspace pulmonary edema associated with thickening of interlobular septa in hydrostatic pulmonary edema. n D  iffuse alveolar damage in acute respiratory distress syndrome and acute interstitial pneumonia. n F  illing of the airspace with blood in diffuse pulmonary hemorrhage. n P  ulmonary capillaritis in patients with underlying ­imm­unologic disorders such as Goodpasture syndrome.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

CT is superior to radiography in demonstrating the presence and extent of abnormalities and the presence of complications. n H  igh-resolution CT findings are relatively nonspecific.

causes of diffuse consolidation are edema, pneumonia, acute respiratory distress syndrome, and hemorrhage. n A  cute interstitial pneumonia is a rare fulminant disease of unknown etiology that usually occurs in a previously healthy person and manifests as clinical, radiologic, and pathologic findings of acute respiratory distress syndrome.

CLINICAL PRESENTATION

Suggested Readings

n D  yspnea

Gluecker T, Capasso P, Schnyder P, et al: Clinical and radiologic features of pulmonary edema. RadioGraphics 19:1507-1531, 1999.

Utility

n H  igh-resolution

n H  emoptysis

in diffuse pulmonary hemorrhage

n A  cute

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n R  adiologic n T  he

10

appearance of extensive or diffuse bilateral consolidation is often similar regardless of cause. differential diagnosis greatly influenced by the clinical history and immune status of the patient.

CONSOLIDATION

Figure 1.  Hydrostatic pulmonary edema. Posteroanterior chest radiograph shows extensive consolidation with relative sparing of the subpleural regions. A permanent pacemaker and an endotracheal tube are in place. The patient was a 63-year-old man with recurrent episodes of acute left-sided heart failure.

Figure 3.  Perihilar distribution of pulmonary edema. Highresolution CT image shows consolidation and ground-glass opacities in the lower lobes. Also noted are mild interlobular septal thickening (arrows) and small pleural effusions. The patient was a 45-year-old man with acute hydrostatic pulmonary edema due to left-sided heart failure.

Ichikado K, Suga M, Muranaka H, et al: Prediction of prognosis for acute respiratory distress syndrome with thin-section CT: Validation in 44 cases. Radiology 238:321-329, 2006. Johkoh T, Müller NL, Taniguchi H, et al: Acute interstitial pneumonia: Thin-section CT findings in 36 patients. Radiology 211:859863, 1999.

Diffuse Consolidation: Acute Causes    11

Figure 2.  Acute respiratory distress syndrome. Anteroposterior chest radiograph shows extensive bilateral areas of consolidation. The patient was a 71-year-old man with acute respiratory distress syndrome. He was intubated shortly after obtaining the chest radiograph.

Figure 4.  Acute respiratory distress syndrome. High-resolution CT image shows bilateral consolidation with air bronchograms in the dependent regions of the lungs. Also noted are extensive ground-glass opacities with superimposed smooth septal thickening (“crazy-paving” pattern). The patient was a 71-year-old man with acute respiratory distress syndrome.

Primack SL, Miller RR, Müller NL: Diffuse pulmonary hemorrhage: Clinical, pathologic, and imaging features. AJR Am J Roentgenol 164:295-300, 1995.

Diffuse Consolidation: Chronic Causes DEFINITION: Diffuse consolidation is replacement of gas within the airspaces by fluid, protein, cells, or other material throughout most of the lungs. IMAGING

DIAGNOSTIC PEARLS

Radiography

n C  hronic

Findings

n O  rganizing

pneumonia: typically multifocal consolidation; occasionally may be diffuse. n C  hronic eosinophilic pneumonia: typically involving mainly peripheral lung and upper lobes (reverse pulmonary edema pattern). n A  lveolar proteinosis: bilateral areas of consolidation that have a vaguely nodular appearance and in up to 50% of cases is perihilar (bat wing or butterfly distribution). Utility

n H  elpful

in demonstrating presence and extent of abnormalities. n L  imited value in the differential diagnosis.

CT

eosinophilic pneumonia: upper lobe ­ redominance, peripheral distribution pattern. p n Organizing  pneumonia: peribronchial and ­peripheral distribution, reversed halo sign.

PATHOLOGY n C  hronic

eosinophilic pneumonia: abundant accumulation of eosinophils in pulmonary interstitium and airspaces. n O  rganizing pneumonia: presence of buds of loose granulation tissue within alveolar ducts and air spaces. n A  lveolar proteinosis: accumulation of protein- and lipid-rich material resembling surfactant within the parenchymal airspaces.

Findings

n O  rganizing

pneumonia: bilateral consolidation, peripheral, perilobular, and peribronchial distribution, reversed halo sign, and ground-glass opacities. n C  hronic eosinophilic pneumonia: bilateral parenchymal consolidation mainly peripheral lung regions (“the photographic negative of pulmonary edema”). Utility

n S  uperior

to radiography in showing distribution of disease and in the differential diagnosis.

CLINICAL PRESENTATION n C  ough

and progressive shortness of breath. of asthma and peripheral eosinophilia common in chronic eosinophilic pneumonia.

n H  istory

DIFFERENTIAL DIAGNOSIS n C  hronic

eosinophilic pneumonia pneumonia of known etiology n C  ryptogenic organizing pneumonia n P  ulmonary alveolar proteinosis n O  rganizing

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  hronic

diffuse pulmonary consolidation is much less common than acute diffuse consolidation. n P  atterns tend to be multifocal rather than diffuse. n C  ryptogenic organizing pneumonia, secondary organizing pneumonia, and eosinophilic lung disease may occasionally be diffuse. n A  lveolar proteinosis is an uncommon condition of unknown etiology that is often diffuse. n O  ccasionally, alveolar proteinosis may be secondary to inhalation of large quantities of silica dust (silicoproteinosis) or be seen in association with marked immunosuppression.

Suggested Readings Chung MJ, Lee KS, Franquet T, et al: Metabolic lung disease: Imaging and histopathologic findings. Eur J Radiol 54:233-245, 2005. Jeong YJ, Kim KI, Seo IJ, et al: Eosinophilic lung diseases: A clinical, radiologic, and pathologic overview. RadioGraphics 27:617-637, 2007. Lee KS, Kim EA: High-resolution CT of alveolar filling disorders. Radiol Clin North Am 39:1211-1230, 2001. Lee KS, Kullnig P, Hartman TE, Müller NL: Cryptogenic organizing pneumonia: CT findings in 43 patients. AJR Am J Roentgenol 162:543-546, 1994.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n Radiologic n It

12

appearance of extensive or diffuse bilateral consolidation is often similar regardless of cause. is essential to know clinical history, laboratory findings, and immune status of patient.

CONSOLIDATION

Figure 1.  Cryptogenic organizing pneumonia. Posteroanterior chest radiograph shows patchy bilateral areas of consolidation and ground-glass opacities. The patient was a 50-year-old woman with cryptogenic organizing pneumonia.

Figure 3.  Cryptogenic organizing pneumonia. High-resolution CT in a 58-year-old immunocompromised woman with organizing pneumonia shows extensive bilateral ground-glass opacities, a few small nodular opacities, and bilateral crescentic and ring-like consolidation (arrows) surrounding areas of ground-glass opacification (reversed halo sign).

Diffuse Consolidation: Chronic Causes    13

Figure 2.  Chronic eosinophilic pneumonia. Posteroanterior chest radiograph shows bilateral areas of consolidation involving the peripheral regions of the upper and middle lung zones. The patient was a 48-year-old woman with chronic eosinophilic pneumonia.

Figure 4.  Chronic eosinophilic pneumonia. High-resolution CT image shows bilateral peripheral areas of consolidation. The patient was a 48-year-old woman with chronic eosinophilic pneumonia.

Central Consolidation (Butterfly or Bat Wing Distribution) DEFINITION: Central consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material with bilateral distribution mainly in the central two thirds of the lungs. IMAGING

DIAGNOSTIC PEARLS

Radiography

n A  cute

Findings n F  airly

homogeneous opacity associated with obscuration of pulmonary vessels and little or no volume loss. n O  bscures adjacent soft tissue structures.

causes: Hydrostatic pulmonary edema, diffuse pulmonary hemorrhage. n C  hronic causes: Organizing pneumonia, alveolar proteinosis.

Utility

n U  sually

only imaging modality used in the assessment of these patients. n H  igh sensitivity and specificity.

CT

Findings

n B  ilateral

ground-glass opacities with superimposed interlobar septal thickening and intralobular lines (“crazy-paving” pattern). n P  erihilar and gravitational distribution of edema. n P  ossible association with severe edema of areas of consolidation involving mainly the dependent lung regions. n “  Crazy-paving” pattern also seen in alveolar proteinosis and pulmonary hemorrhage. n P  eribronchial consolidation noted in bronchiolitis obliterans organizing pneumonia. Utility

n S  uperior

to radiography in showing the pattern and extent of abnormalities

CLINICAL PRESENTATION n D  yspnea,

cough in diffuse pulmonary hemorrhage

n C  ryptogenic

organizing pneumonia pneumonia reaction pattern n B  ronchopneumonia n P  neumocystis pneumonia n A  lveolar proteinosis n O  rganizing

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  ommon

manifestation of hydrostatic pulmonary edema. n C  ommonly seen in patients with fluid overload associated with renal failure. n R  elatively common in Pneumocystis pneumonia. n O  ccasionally seen in bronchiolitis obliterans organizing pneumonia and alveolar proteinosis.

Suggested Readings Gluecker T, Capasso P, Schnyder P, et al: Clinical and radiologic features of pulmonary edema. RadioGraphics 19:1507-1531, 1999. Primack S, Miller RR, Muller NL: Diffuse pulmonary hemorrhage: Clinical, pathologic, and imaging features. AJR Am J Roentgenol 164:295-300, 1995. Storto ML, Kee ST, Golden JA: Hydrostatic pulmonary edema: Highresolution CT findings. AJR Am Roentgenol 165:817-820, 1995.

n H  emoptysis

DIFFERENTIAL DIAGNOSIS n H  ydrostatic n D  iffuse

pulmonary edema pulmonary hemorrhage

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n R  adiologic

appearance of extensive or diffuse bilateral consolidation is often similar regardless of cause. is essential to know the clinical history (e.g., trauma, known systemic disease), presence of fever, and immune status of patient.

n I t

14

CONSOLIDATION

Central Consolidation (Butterfly or Bat Wing Distribution)    15

Figure 1.  Bat wing pattern of pulmonary edema. Posteroanterior radiograph shows consolidation of the perihilar and medullary portions of both lungs, creating a bat wing or butterfly appearance; the cortex of both lungs is relatively unaffected. The consolidation is fairly homogeneous and is associated with well-defined air bronchograms on both sides. Also noted is a central venous line. The patient was a 38-year-old man with severe acute hydrostatic pulmonary edema.

Figure 2.  Pneumocystis jiroveci pneumonia. Posteroanterior chest radiograph shows bilateral areas of consolidation and ground-glass opacities in a predominantly perihilar distribution. The patient was a 32-year-old with AIDS and P. jiroveci pneumonia.

Figure 3.  Perihilar distribution of pulmonary edema. Highresolution CT image shows consolidation and ground-glass opacities in the lower lobes. Also noted are mild interlobular septal thickening (arrows) and small pleural effusions. The patient was a 45-year-old man with acute hydrostatic pulmonary edema due to left-sided heart failure.

Peripheral Consolidation (Reverse Pulmonary Edema Pattern) DEFINITION: Peripheral consolidation is replacement of gas within airspaces by fluid, protein, cells, or other material predominantly in the outer third of the lungs. IMAGING

DIAGNOSTIC PEARLS

Radiography

n C  ryptogenic

Findings

n B  ilateral

parenchymal consolidation involves mainly the peripheral lung regions (“photographic negative of pulmonary edema”). n M  ay be seen in chronic eosinophilic pneumonia, cryptogenic organizing pneumonia (idiopathic bronchiolitis obliterans organizing pneumonia), and, less commonly, pneumonia, acute respiratory distress syndrome, sarcoidosis, and bronchioloalveolar carcinoma. n P  eripheral distribution, involving mainly upper lobes, is apparent in approximately 60% of patients with chronic eosinophilic pneumonia. n P  eripheral consolidation is apparent on the radiograph in a small percentage of patients with cryptogenic organizing pneumonia. Utility

n H  elpful

in showing presence, distribution, and extent of parenchymal abnormalities.

CT

Findings

n B  ilateral

parenchymal consolidation. mainly the peripheral lung regions (“photographic negative of pulmonary edema”). n O  ften middle and upper lung zone predominance in chronic eosinophilic pneumonia. n G  round-glass opacities adjacent to areas of consolidation. n P  eripheral consolidation evident on CT in 60%-80% of patients with cryptogenic organizing pneumonia, mainly involving the middle and lower lung zones. n I nvolves

Utility

n S  uperior

to radiography in determining the peripheral distribution of the consolidation particularly in patients with chronic eosinophilic pneumonia and cryptogenic organizing pneumonia.

CLINICAL PRESENTATION n C  ough

and progressive shortness of breath. n L  ow-grade fever common in chronic eosinophilic pneumonia and cryptogenic organizing pneumonia. n H  istory of atopy or asthma in approximately 50% of patients with chronic eosinophilic pneumonia.

organizing pneumonia: Peribronchial and peripheral distribution, reverse halo sign. n C  hronic eosinophilic pneumonia: Upper lobe ­predominance. n U  ncommon causes: Sarcoidosis, bronchioloalveolar carcinoma, and Churg-Strauss syndrome.

n P  eripheral

eosinophilia in majority of patients with chronic eosinophilic pneumonia.

DIFFERENTIAL DIAGNOSIS n C  ryptogenic

organizing pneumonia pneumonia of known etiology n C  hronic eosinophilic pneumonia n S  arcoidosis n C  hurg-Strauss syndrome n B  ronchioloalveolar carcinoma n O  rganizing

PATHOLOGY n C  hronic

eosinophilic pneumonia: abundant accumulation of eosinophils in the pulmonary interstitium and airspaces; may be manifestation of Churg-Strauss syndrome. n E  osinophilic vasculitis seen almost exclusively in patients with asthma. n O  rganizing pneumonia: intraluminal plugs of granulation tissue within alveolar ducts and surrounding alveoli with or without concomitant granulation tissue polyps within the respiratory bronchioles.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  pproximately

50% of patients with chronic eosinophilic pneumonia have history of atopy, most often asthma, and most have peripheral eosinophilia.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n R  adiologic

appearance of bilateral consolidation is often similar regardless of cause. is essential to know clinical history (e.g., known systemic disease), presence of fever, and immune status of patient.

n I t

16

CONSOLIDATION

Peripheral Consolidation (Reverse Pulmonary Edema Pattern)    17

Figure 2.  Peripheral consolidation in chronic eosinophilic pneumonia. High-resolution CT image shows bilateral peripheral areas of consolidation. The patient was a 48-year-old woman with chronic eosinophilic pneumonia. Figure 1.  Peripheral consolidation in chronic eosinophilic pneumonia. Posteroanterior chest radiograph shows bilateral areas of consolidation involving the peripheral regions of the upper and middle lung zones. The patient was a 48-year-old woman with chronic eosinophilic pneumonia.

Figure 3.  Peripheral consolidation in cryptogenic organizing pneumonia. High-resolution CT image shows bilateral peripheral and peribronchial areas of consolidation in the upper lobes. The patient was a 55-year-old woman with cryptogenic organizing pneumonia.

Suggested Readings Allen JN, Davis WB: Eosinophilic lung diseases. Am J Respir Crit Care Med 150:1423-1438, 1994. Cordier JF: Cryptogenic organising pneumonia. Eur Respir J 28:422446, 2006.

Figure 4.  Peribronchial and peripheral consolidation in cryptogenic organizing pneumonia. High-resolution CT image shows bilateral areas of consolidation in a peribronchial (arrows) and subpleural distribution. The patient was a 34-year-old man with cryptogenic organizing pneumonia.

Kim Y, Lee KS, Choi DC, et al: The spectrum of eosinophilic lung disease: Radiologic findings. J Comput Assist Tomogr 21:920-930, 1997. Lynch DA, Travis WD, Müller NL, et al: Idiopathic interstitial pneumonias: CT features. Radiology 236:10-21, 2005.

Part 2 

ATELECTASIS

Atelectasis DEFINITION:  Atelectasis is defined as less than normal inflation of all or part of the lung with ­corresponding diminution in lung volume.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n D  isplacement

Findings n D  irect

signs: displaced interlobar fissures, crowding of vessels and bronchi. n I ndirect signs: increased opacity; displacement of hilum, mediastinum, hemidiaphragm; tenting (juxtaphrenic peak) of hemidiaphragm; compensatory overinflation of remaining lung. n S  ilhouette sign: obliteration of right-sided heart border in right middle lobe atelectasis and left cardiac border/ mediastinum in left upper lobe atelectasis. n L  uftsichel: a crescent of hyperlucency (“air crescent”) adjacent to aortic arch in left upper lobe atelectasis. n R  ound atelectasis: bronchi and vessels gather in curvilinear fashion as they pass toward pleural-based nodular opacity or mass (comet tail sign). n L  inear soft tissue opacities of 1-3 mm thickness and 4-10 cm in length in mid and lower lung zone. Utility

n H  igh

sensitivity and specificity in diagnosis of atelectasis.

CT

Findings n D  irect

signs: displaced interlobar fissures, crowding of vessels and bronchi within the atelectatic lobe. n I ndirect signs: increased opacity, displacement of hilum, mediastinum, hemidiaphragm; tenting (juxtaphrenic peak) of hemidiaphragm; compensatory overinflation of remaining lung. n R  ound atelectasis: peripheral “mass” abutting area of thickening pleura, associated with volume loss, and bronchi and vessels gathering in curvilinear fashion as they pass toward pleural-based nodular opacity or mass (comet tail sign). n D  ependent atelectasis: ill-defined area of increased attenuation/subpleural curvilinear opacities in dorsal

of the fissures that form the ­ oundary of atelectatic lobe. b n C  rowding of vessels and bronchi visible within area of atelectasis. n I ncreased opacity accompanied by diaphragmatic elevation, mediastinal shift, and overinflation of remainder of unaffected lung.

lung regions that typically resolves when patient is prone.

Utility

n P  rovides

valuable additional information in obstructive atelectasis with regard to location and extent. n D  istinguishes proximal obstructing tumor from collapsed lung/adjacent mediastinal structures with intravenous contrast material. n D  ifferentiates dependent atelectasis from interstitial/ airspace disease by scanning with patient in supine and prone position.

CLINICAL PRESENTATION n P  atient

n C  ough,

may be asymptomatic. dyspnea.

DIFFERENTIAL DIAGNOSIS n D  iffuse

consolidation: Acute causes consolidation: Chronic causes n F  ocal consolidation: Acute causes n F  ocal consolidation: Chronic causes n L  obar pneumonia n A  cute pulmonary embolism n A  spiration pneumonia n D  iffuse

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n L  ack

of air bronchograms within atelectatic lung is suggestive of bronchial obstruction (resorptive ­ telectasis). a n C  T, particularly contrast-enhanced CT, often provides valuable additional information in patients with obstructive atelectasis, particularly with regard to the precise location and extent of the obstructing process. n R  ound atelectasis is seen most commonly in patients with asbestos-related pleural disease. n T  he diagnosis of rounded atelectasis can often be made confidently on CT.

18

ATELECTASIS

Atelectasis    19

Figure 2.  Direct and indirect signs of atelectasis. Contrastenhanced CT image shows cephalad and medial displacement of the minor fissure (arrows). Also note presence of mediastinal lymphadenopathy. The patient was a 47-year-old man with right upper lobe atelectasis due to endobronchial pulmonary carcinoma.

Figure 1.  Direct and indirect signs of atelectasis. View from a chest radiograph shows cephalad and medial displacement of the minor fissure (straight arrows), a direct sign of right upper lobe atelectasis. Also note several indirect signs, including increased opacity of the atelectatic lobe, superior displacement of the right hilum, lateral displacement of the right interlobar pulmonary artery (curved arrow), and elevation of the right hemidiaphragm. The patient was a 47-year-old man with right upper lobe atelectasis due to endobronchial pulmonary carcinoma.

Figure 3.  Round atelectasis. High-resolution CT image shows irregular mass in the left upper lobe with band-like opacities extending toward an area of pleural thickening. Also note volume loss of the left upper lobe causing curvilinear anterior displacement of the left major fissure (straight arrow). The patient was a 75-year-old man with a history of asbestos exposure.

Figure 4.  Round atelectasis. Magnified view of the left lung from a posteroanterior chest radiograph shows an oval opacity. The lateral margins (straight arrows) are well defined (where the opacity abuts the lung) and the medial margins are poorly defined (where the opacity abuts the pleura). Pulmonary vessels (curved arrows) can be seen to curve toward the opacity (comet tail sign). The patient was a 71-year-old man with asbestosrelated pleural plaques and round atelectasis.

20     Atelectasis

PATHOLOGY n O  bstructive/resorptive

atelectasis: air flow to region of lung interrupted due to airway obstruction. n L  oss of volume as lung retracts in presence of pneumothorax. n C  ompression of lung by adjacent space-occupying ­process. n D  eficiency in surfactant increases surface tension of alveoli; increase in distending pressure. n R  etraction of fibrous tissue as it matures, resulting in volume loss of affected portion of lung.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n S  egmental, lobar, and whole-lung atelectasis is commonly

due to bronchial obstruction by secretions or tumor.

ATELECTASIS

n M  ost

cases of round atelectasis are seen in patients exposed to asbestos. n L  ower left lobe atelectasis occurs in the majority of patients after ­cardiac surgery.

Suggested Readings Lee KS, Logan PM, Primack SL, Müller NL: Combined lobar atelectasis of the right lung: Imaging findings. AJR Am J Roentgenol 163:43-47, 1994. Molina PL, Hiken JN, Glazer HS: Imaging evaluation of obstructive atelectasis. J Thorac Imag 11:176-186, 1996. Proto AV: Lobar collapse: Basic concepts. Eur J Radiol 23:9-22, 1996. Woodring JH, Reed JC: Types and mechanisms of pulmonary atelectasis. J Thorac Imag 11:92-108, 1996. Woodring JH, Reed JC: Radiographic manifestations of lobar atelectasis. J Thorac Imag 11:109-144, 1996.

Lobar Atelectasis DEFINITION: Lobar atelectasis is less than normal inflation of all or part of the lung with ­corresponding diminution in lung volume.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n D  isplacement

Findings n D  irect

signs: displaced interlobar fissures, crowded air bronchograms. n I ndirect signs: increased opacity; displacement of hilum, mediastinum, hemidiaphragm; tenting (juxtaphrenic peak) of hemidiaphragm; compensatory overinflation of remaining lung. n L  eft upper lobe atelectasis: left major fissure shifted cephalad and anteriorly seen on the lateral view; overinflated superior segment often resulting in hyperlucent crescent adjacent to aortic arch (“Luftsichel” sign) on frontal view. n R  ight middle lobe atelectasis: approximation of minor fissure and lower half of major fissure seen on the lateral radiograph; obscuration of right-sided heart border on frontal view. n C  ombined right middle and lower lobe atelectasis: major and minor fissures displaced downward and backward so that opacity occupies posteroinferior portion of hemithorax; right hemidiaphragm obscured by atelectatic right lower lobe; right-sided heart border obscured by atelectatic right middle lobe. n C  ombined right middle and upper lobe atelectasis: findings similar to those of left upper lobe atelectasis. n O  bstructive lobar atelectasis typically associated with increased opacity of atelectatic lobe and lack of air bronchograms. n H  ilar tumor with distal atelectasis typically shown by S sign of Golden, with a downward bulge in medial portion and concave appearance of lateral portion of interlobar fissure; most commonly seen in association with right upper lobe atelectasis. Utility

n F  irst

and often only imaging modality used in assessment of patients with lobar atelectasis.

CT

Findings

signs: displaced interlobar fissures, crowded air bronchograms. n I ndirect signs: increased opacity; displacement of hilum, mediastinum, hemidiaphragm; tenting (­juxtaphrenic peak) of hemidiaphragm usually related to presence of inferior

of interlobar fissures is a direct sign of atelectasis. n P  atterns of atelectasis of right and left upper lobes differ because there is no minor fissure on the left. n F  indings of right lower lobe atelectasis are similar to those of left lower lobe atelectasis. n R  ight middle lobe atelectasis is often detectable only on the lateral radiograph or CT.

accessory fissure; compensatory overinflation of remaining lung. n O  ften demonstrates cause of atelectasis. Utility

n P  rovides

valuable additional information in patients with obstructive atelectasis, regarding precise location and extent of obstructing process.

MRI

Findings

n D  ecreased

volume and increased signal intensity of atelectatic lobe.

Utility

n M  ay

be helpful in assessment of obstructive atelectasis due to central tumor.

CLINICAL PRESENTATION n P  atients

may be asymptomatic. symptoms are cough and shortness of breath in patients with acute atelectasis due to bronchial obstruction by mucus, aspiration, or foreign body. n C  hronic cough and, occasionally, hemoptysis occur in patients with lobar atelectasis due to bronchiectasis or endobronchial tumor. n A  cute

n D  irect

DIFFERENTIAL DIAGNOSIS n L  obar

n S  ingle

pneumonia and multiple pulmonary masses

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n D  isplacement

of fissures that form boundaries of atelectatic lobes is a dependable and easily recognized sign of atelectasis. n C  T is commonly helpful in demonstrating cause of atelectasis. n C  ontrast-enhanced CT is particularly helpful in demonstrating central obstructing tumors.

21

22     Lobar Atelectasis

Figure 1.  Right middle lobe atelectasis. Posteroanterior radiograph shows poorly defined area of increased attenuation, associated with obscuration of the right-sided heart border (“silhouette” sign).

Figure 3.  Right middle lobe atelectasis. Lateral view shows downward shift of the minor fissure and forward shift of the right major fissure, leading to a triangular area of increased opacity (arrow) characteristic of right middle lobe atelectasis.

ATELECTASIS

Figure 2.  Right middle lobe atelectasis. High-resolution CT image shows characteristic broad triangular configuration of atelectatic right middle lobe. The anterior border of the atelectatic lobe is outlined by the minor fissure, which is displaced downward (arrow), and the posterior border by the major fissure, which is displaced upward and forward (arrowhead). The patient was a 72-year-old woman with chronic right middle lobe atelectasis secondary to bronchiectasis.

Figure 4.  Left lower lobe atelectasis. Chest radiograph shows inferior and medial displacement of the left major fissure resulting in a well-defined interface (arrow) extending obliquely downward and laterally from the region of the hilum, characteristic of left lower lobe atelectasis. The atelectatic left lower lobe obscures the silhouette of the left descending pulmonary artery and the left hemidiaphragm. The patient was a 69-year-old woman with asthma.

Lobar Atelectasis    23

ATELECTASIS

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n H  ilar

displacement occurs more commonly in atelectasis of upper than lower lobes. n D  ownward displacement of right hilum in cases of lower lobe atelectasis is seldom clearly appreciated. n D  ownward displacement of only the left hilum is seen in only 3% of normal individuals. n C  ombined right upper and middle lobe atelectasis occurs most commonly with mucus plugs and pulmonary carcinoma. n L  ess commonly, right upper and middle lobe collapse occur with carcinoid tumors, metastatic tumors, and inflammatory processes. n C  ombined right upper and lower lobe atelectasis is rare. n A  telectasis is seen in a majority of patients after cardiac surgery.

Suggested Readings Davis SD, Yankelevitz DF, Wand A, Chiarella DA: Juxtaphrenic peak in upper and middle lobe volume loss: Assessment with CT. Radiology 198:143-149, 1996. Lee KS, Logan PM, Primack SL, Müller NL: Combined lobar atelectasis of the right lung: Imaging findings. AJR Am J Roentgenol 163:43-47, 1994. Naidich DP, McCauley DI, Khouri NF, et al: Computed tomography of lobar collapse: 1. Endobronchial obstruction. J Comput Assist Tomogr 7:745-757, 1983. Proto AV: Lobar collapse: Basic concepts. Eur J Radiol 23:9-22, 1996. Woodring JH, Reed JC: Types and mechanisms of pulmonary atelectasis. J Thorac Imag 11:92-108, 1996. Woodring JH, Reed JC: Radiographic manifestations of lobar atelectasis. J Thorac Imag 11:109-144, 1996.

Round Atelectasis DEFINITION: Round atelectasis is a distinct form of atelectasis characteristically associated with ­focal pleural thickening.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n H  omogeneous

Findings n F  airly

homogeneous round, oval, wedge-shaped, or irregularly shaped mass in peripheral lung adjacent to thickened pleura. n C  omet tail sign. n U  sually Measures 3.0-6.0 cm in greatest diameter.

round, oval, wedge-shaped, or i­rregularly shaped mass in the peripheral lung adjacent to thickened pleura. n C  omet tail sign. n A  telectasis proportional to the size of the mass. n M  ass represents atelectatic lung.

Utility

n H  elpful

in demonstrating presence of abnormality but of limited value in specific diagnosis.

CT

Findings n C  omet

tail sign occurs when vessels and bronchi curve into periphery of mass. n B  ronchi and vessels curve and converge toward a round/oval mass that abuts an area of pleural thickening. n E  vidence of volume loss occurs in affected lobe. n S  ubpleural fat may be identified within the mass, a feature that reflects chronicity. n L  ung parenchyma adjacent to round atelectasis shows compensatory hyperinflation. Utility n C  T

diagnostic in most cases. requires that round atelectasis be adjacent to thickened pleura, with vessels and bronchi curving into the periphery of the “mass”; lung volume loss is proportional to the size of “mass.” n M  ultiplanar reconstructed images are helpful in better determining the course of blood vessels and bronchi in these cases. n D  iagnosis

n P  ulmonary

vessels and bronchi converge toward area of atelectasis (comet tail sign), which is often best seen on sagittal/oblique sagittal images.

Utility n O  f

limited value in assessment of round atelectasis.

Positron Emission Tomography Findings n L  ittle

Utility

or no uptake

n H  elpful

noma.

in distinguishing round atelectasis from carci-

CLINICAL PRESENTATION n U  sually

asymptomatic

DIFFERENTIAL DIAGNOSIS n P  ulmonary

n G  ranuloma

carcinoma

n I nflammatory

pseudo-tumor

PATHOLOGY

MRI

Findings n S  ignal

intensity is higher than that of muscle and lower than that of fat on T1-weighted images and similar to or lower than that of fat on T2-weighted images. n A  telectatic mass enhances homogeneously after administration of gadopentetate dimeglumine.

n P  leural-based

mass that consists of atelectasis associated with pleural fibrosis. n S  een most commonly in patients exposed to asbestos. n O  ther causes: pleural effusion from tuberculosis, infections other than tuberculosis, pulmonary infarction, left-sided heart failure, surgery (mainly cardiac), malignant tumor.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n C  T

findings are often sufficiently characteristic that neither biopsy nor further investigative procedures are necessary to exclude more ominous disease. n P  ET typically shows no uptake. n N  eedle biopsy may occasionally be required to rule out carcinoma. n F  ollow-up of patients who have round atelectasis has shown that the majority of lesions are stable for many years. n O  ccasionally, a lesion decreases in size, resolves within a few weeks to several years, or enlarges.

24

ATELECTASIS

Round Atelectasis    25

Figure 1.  Round atelectasis. A high-resolution CT scan shows an irregular mass in the left upper lobe with band-like opacities extending toward an area of pleural thickening. Also note the volume loss in the left upper lobe causing curvilinear anterior displacement of the left major fissure (arrow). The patient was a 75-year-old man with a history of asbestos exposure.

Figure 2.  Round atelectasis. Soft tissue windows demonstrate bilateral calcified pleural plaques (arrowheads). The patient was a 75-year-old man with a history of asbestos exposure.

Figure 3.  Round atelectasis. A high-resolution CT scan at a more cephalad level than in Figures 1 and 2 shows pulmonary vessels (curved arrow) curving toward the area of pleural thickening. Also noted are superior and anterior displacement of the left major fissure (straight arrow) and a right pleural plaque (arrowhead). The patient was a 75-year-old man with a history of asbestos exposure.

Figure 4.  Round atelectasis. A coronal maximum intensity projection reformatted image shows the pulmonary vessels curving toward the left upper lobe mass and superior displacement of the left major fissure. The patient was a 75-year-old man with a history of asbestos exposure.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n S  een

most commonly in patients with asbestos-related pleural plaques or diffuse pleural thickening.

Suggested Readings Batra P, Brown K, Hayashi K, Mori M: Rounded atelectasis. J Thorac Imaging 11:187-197, 1996.

Hillerdal G: Rounded atelectasis: Clinical experience with 74 patients. Chest 95:836-941, 1989. Ludeman N, Elicker BM, Reddy GP, et al: Atypical rounded atelectasis: Diagnosis and management based on results of F-18 FDG positron emission tomography. Clin Nucl Med 30:734-735, 2005. McHugh K, Blaquiere RM: CT features of rounded atelectasis. AJR Am J Roentgenol 153:257-260, 1989. Yamaguchi T, Hayashi K, Ashizawa K, et al: Magnetic resonance ­imaging of rounded atelectasis. J Thorac Imaging 12:188-194, 1997.

Mediastinal Shift DEFINITION: Mediastinal shift is deviation of the mediastinum and its contents away from its normal midline location. IMAGING

DIAGNOSTIC PEARLS

Radiography

n I psilateral

Findings

n A  telectasis

of lung or lobe: ipsilateral shift of mediasti­ num and trachea. n P  ulmonary agenesis/aplasia/severe hypoplasia: ab­­ sence of aerated lung in one hemothorax; ipsilateral hemidiaphragm elevation; ipsilateral mediastinal shift; rib approximation. n S  wyer-James-McLeod syndrome: hyperlucent lobe/ lung, decreased vascularity of involved lobe/lung, normal/decreased size of involved lobe/lung, and decreased size of ipsilateral hilum. n P  ectus excavatum: obscuration of right-sided heart border; displacement of heart to left hemithorax. n C  ontralateral shift of mediastinum in large pneumo­ thorax, pleural effusion, or pleural malignancy. n C  ontralateral shift in large pulmonary space-occupying lesion, such as tumor, cyst, congenital cystic adeno­ matoid malformation, congenital lobar emphysema, or bulla(e).

CT

Findings

n A  telectasis

of lung or lobe: ipsilateral shift of mediasti­ num and trachea. n P  ulmonary agenesis/aplasia/severe hypoplasia: ab­­ sence of aerated lung in one hemothorax; ipsilateral hemidiaphragm elevation; ipsilateral mediastinal shift; rib approximation. n S  wyer-James-McLeod syndrome: hyperlucent lobe/ lung, decreased attenuation and vascularity of involved lobe/lung, normal/decreased size of involved lobe/ lung on inspiration, and air trapping on expiration. n C  ontralateral shift of mediastinum in large pneumo­ thorax, pleural effusion, pleural malignancy. n C  ontralateral shift in large pulmonary space-occupying lesion such as tumor, cyst, congenital cystic adenoma­ toid malformation, congenital lobar emphysema, or bulla(e). n C  ongenital cystic adenomatoid malformation: unilocu­ lar/multiloculated cyst or complex soft tissue and cys­ tic mass ranging from 4-12 cm in diameter.

shift: Atelectasis, fibrothorax, ­ esothelioma m n C  ontralateral shift: Pleural effusion, ­pneumothorax, large tumor, mesothelioma Utility

n A  llows

diagnosis of pulmonary agenesis, aplasia, and hypoplasia.

CLINICAL PRESENTATION n P  atients

may be asymptomatic or have nonspecific symptoms of cough and shortness of breath. n S  wyer-James-McLeod syndrome: majority of patients are asymptomatic; occasionally they may present with a history of recurrent respiratory tract infections or shortness of breath. n A  cute shortness of breath and pleuritic chest pain occur in pneumothorax. n W  eight loss and progressive shortness of breath occur in pulmonary or pleural malignancy.

DIFFERENTIAL DIAGNOSIS n A  telectasis

of lobe or lung

n F  ibrothorax n L  obectomy

or pneumonectomy effusion n P  neumothorax n M  esothelioma n P  leural

PATHOLOGY n M  ediastinal

shift is away from space-occupying abnor­ malities such as large pleural effusion, pleural malig­ nancy, large lung tumor, or mass. n M  ediastinal shift is toward hemithorax with decreased volume due to atelectasis, fibrothorax, or mesothe­lioma. n A  nterior and middle mediastinal compartments are more mobile than posterior compartment, with shift to greater extent in patients with atelectasis.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n M  ediastinal

shift is often helpful in recognizing presence of pulmonary or pleural abnormality. shift is most commonly due to atelectasis. n C  ontralateral mediastinal shift is most commonly due to pneumothorax or large pleural effusion. n P  leural malignancy, including mesothelioma and metastasis, may result in ipsilateral or contralateral ­mediastinal shift. n L  arge pleural effusions associated with mediastinal shift are most commonly due to infection or neoplasm. n M  ediastinal

26

Mediastinal Shift    27

ATELECTASIS

Figure 1.  Obstructive atelectasis of right lung. Chest radiograph shows opacification and decreased volume of the right hemithorax. The trachea and mediastinum are shifted to the right and the left lung shows compensatory overinflation. The lack of air bronchograms within the opacified atelectatic right lung is consistent with obstructive atelectasis. The patient was a 44-yearold man with squamous cell carcinoma.

Figure 3.  Obstructive atelectasis of right lung. Contrastenhanced CT demonstrates complete obstruction of the right main bronchus by tumor (arrow) and distal atelectasis and obstructive pneumonitis. Note that the descending aorta is essentially in its normal position while the anterior and middle mediastinum are markedly displaced to the right. The patient was a 44-year-old man with squamous cell carcinoma.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ediastinal

shift is most commonly due to atelectasis. mediastinal shift is most commonly due to pneumothorax or large pleural effusion.

n C  ontralateral

Figure 2.  Swyer-James-McLeod syndrome. Chest radiograph shows hyperlucency and decreased vascularity of the left lung. The mediastinum is shifted to the left consistent with decreased left lung volume. The patient was a 40-year-old man with SwyerJames-McLeod syndrome.

Figure 4.  Swyer-James-McLeod syndrome. High-resolution CT shows decreased attenuation and vascularity of the left lung with associated bronchiectasis and mild volume loss leading to ipsilateral shift of the mediastinum and anterior junction line. The patient was a 61-year-old woman with Swyer-James-McLeod syndrome.

Suggested Readings Moore ADA, Godwin JD, Dietrich PA, et al: Swyer-James syndrome: CT findings in eight patients. AJR Am J Roentgenol 158:1211-1215, 1992. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27(2):193-213, 2006. Woodring JH, Reed JC: Types and mechanisms of pulmonary atelecta­ sis. J Thorac Imag 11:92-108, 1996.

Unilateral Hilar Displacement DEFINITION: Unilateral hilar displacement is upward or downward displacement of the hilum while the medial aspect of the lung usually remains fixed. IMAGING

DIAGNOSTIC PEARLS

Radiography

n Loss

Findings

n E  levation

of hilum in upper lobe atelectasis, scarring, or upper lobectomy. n D  ownward displacement of hilum in lower lobe atelectasis, scarring, or lower lobectomy and in combined middle and lower lobe atelectasis.

of lung volume. displacement in upper lobe atelectasis, scarring or lobectomy. n D  ownward displacement in lower lobe atelectasis, scarring or lobectomy. n U  pward

Utility

n O  ften

first and only imaging modality used in assessment of patient.

CT

Findings

n E  levation

and forward displacement of hilum in upper lobe atelectasis, scarring, or upper lobectomy. n D  ownward and posterior displacement of hilum in lower lobe atelectasis, scarring, or lower lobectomy and in combined middle and lower lobe atel­ectasis. n A  telectatic lobe tapers smoothly toward hilum. n O  bstructive tumor or mass. Utility

n H  elpful

loss.

in demonstrating underlying cause of volume

PATHOLOGY n B  ecause

medial aspect of lung is fixed at hilum, atelectatic forms are affected by relatively rigid lung components (bronchi, arteries, veins). n A  s lobe loses volume, two surfaces approximate, with the end result of total atelectasis being a flattened triangle instead of a normal pyramid. n S  igns related to shift of other structures to compensate for loss of volume include unilateral hilar displacement.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n O  ccurs

CLINICAL PRESENTATION may be asymptomatic or have nonspecific symptoms of cough and dyspnea. n O  ccasionally, hemoptysis due to endobronchial lesion.

more commonly in atelectasis of upper and lower lobes. n B  ecomes more marked as atelectasis becomes chronic.

n P  atients

DIFFERENTIAL DIAGNOSIS n P  ostprimary

tuberculosis atelectasis n L  obectomy n L  obar

Suggested Readings Lee KS, Logan PM, Primack SL, Müller NL: Combined lobar atelectasis of the right lung: Imaging findings. AJR Am J Roentgenol 163:43-47, 1994. Molina PL, Hiken JN, Glazer HS: Imaging evaluation of obstructive atelectasis. J Thorac Imag 11:176-186, 1996. Proto AV: Lobar collapse: Basic concepts. Eur J Radiol 23:9-22, 1996. Woodring JH, Reed JC: Radiographic manifestations of lobar atelectasis. J Thorac Imag 11:109-144, 1996. Woodring JH, Reed JC: Types and mechanisms of pulmonary atelectasis. J Thorac Imag 11:92-108, 1996.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n U  nilateral n H  ilar

28

cephalad or caudal displacement of hila is common manifestation of atelectasis. displacement becomes more marked as atelectasis becomes chronic.

ATELECTASIS

Figure 1.  Elevation of hilum due to previous lobectomy. Chest radiograph shows decrease in size of the right hemithorax, elevation of the right hilum (straight arrow), lateral displacement of the right interlobar pulmonary artery, and tenting of the right hemidiaphragm (curved arrow). The patient was a 73-year-old woman with previous right upper lobectomy.

Unilateral Hilar Displacement    29

Figure 2.  Elevation of hilum due to atelectasis. Posteroanterior chest radiograph shows poorly defined increased opacity of the left hemithorax associated with obliteration of the left-sided heart border (silhouette sign), volume loss of the left hemithorax, elevation of the left hemidiaphragm, and superior displacement of the left hilum characteristic of left upper lobe atelectasis. Note crescent-shaped lucency between the apex of the atelectatic left upper lobe and the aortic arch (Luftsichel sign).

Figure 3.  Combined right middle lobe and lower lobe atelectasis. Posteroanterior chest radiograph shows caudad displacement of the right major (straight arrows) and minor (curved arrow) fissures. Caudal displacement of the right hilum and overinflation of the right upper lobe are also evident. The silhouette of the right atrium is obscured by the atelectatic middle lobe.

Part 3 

NODULES AND MASSES

Solitary Lung Nodule DEFINITION: A pulmonary nodule is any pulmonary lesion characterized by a well-defined, discrete, approximately circular opacity ≤3 cm in diameter. IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  ain

Findings

n I ntrapulmonary

nodule forming an acute angle with contiguous pleura and well-defined margins seen en face. n P  leural or extrapleural nodule that tends to have tapered margins, is poorly defined en face, and forms an obtuse angle with chest wall. n D  iffuse or central (target) calcification in a benign nodule. Utility

within pulmonary nodule is more readily seen on low-kilovoltage than high-kilovoltage radiographs. n P  resence of diffuse or central calcification in a smoothly marginated nodule is virtually diagnostic of a granuloma (tuberculoma, histoplasmoma).

diagnostic radiologic criteria to differentiate benign from malignant nodules: size, change in size over time, calcification, fat, margins. n C  alcification within solitary pulmonary nodule most reliable sign that lesion is benign. n L  ikelihood for malignancy: 0.5- to 1.0-cm diameter, 35%; 2-cm diameter, 50%; 2- to 3-cm diameter, 80%; 3-cm diameter, 95%.

n C  alcification

CT

Findings

n F  at-attenuation

value on thin-section CT within smoothly marginated lung nodule is virtually diagnostic of hamartoma. n F  at within spiculated lesion is most suggestive of focal lipoid pneumonia. n W  ater density and thin or invisible wall are diagnostic of cystic lesion (bronchogenic cyst, congenital cystic adenomatoid malformation, hydatid cyst, fluid-filled bulla). n A  ir bronchograms and air bronchiolograms are seen more commonly with pulmonary carcinomas than with benign nodules. n B  ubble lucencies within nodule are often seen in bronchioalveolar carcinomas, acinar adenocarcinomas, and other malignancies and are uncommon in benign tumors. n N  odule with ground-glass opacity surrounding solid component or with a mixed ground-glass and solid component is more likely to be malignant.

n N  odules

with predominantly solid component tend to be associated with more aggressive tumors.

Utility n C  T

is used routinely for assessment of solitary lung nodule. n C  T is superior to chest radiography in detection and characterization of nodules. n C  T can show if nodule is clearly benign, as determined by rigidly defined radiologic signs, or of indeterminate nature n N  odule detection is optimized by thinner sections, multiplanar and maximum intensity projection reconstructions, and dynamic viewing on workstation. n O  ptimal assessment of lung nodules for presence of calcification by CT requires thin sections (1- to 3-mm collimation).

Positron Emission Tomography Findings

n E  nhancement

lesion.

seen in malignant and inflammatory

Utility

n F  DG-PET

has sensitivity of 97% and specificity of 78% for diagnosis of malignancy in nodules ≥10 mm.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n Clinical

findings to consider include age, risk factors, recent travel history, and symptoms. for malignancy is: 0.5- to 1.0-cm diameter, 35%; 2-cm diameter, 50%; 2- to 3-cm diameter, 80%; 3-cm diameter, 95%. n O  nly two findings are considered to be sufficient to preclude further evaluation: benign pattern of ­calcification and stability in size for more than 2 years. n F  leischner Society recommends schedule of follow-up studies classified by nodule size and presence of risk factor. n T  ransthoracic needle aspiration or biopsy is indicated in patients with solitary lung nodules who cannot/ would not undergo surgery. n Likelihood

30

NODULES AND MASSES

Solitary Lung Nodule    31

Figure 2.  Calcified granuloma with diffuse calcification. A magnified view of the right upper lobe from a frontal chest radiograph shows a diffusely calcified nodule (arrow). The patient was a 70-year-old man with previous tuberculosis.

Figure 1.  Patterns of calcification. A schematic drawing shows the characteristic patterns of pulmonary nodule calcification. Diffuse calcification, central calcification in nodules ≤2.0 cm in diameter, popcorn calcification, and laminated calcification are virtually diagnostic of a benign nodule. Diffuse, central, and laminated types of calcification are seen most commonly in calcified granulomas as a result of previous tuberculosis or histoplasmosis, and popcorn calcification, albeit rare, is virtually diagnostic of hamartoma. Stippled calcification, particularly when seen in large masses, and eccentric calcification are worrisome for malignancy. They occur most commonly in pulmonary carcinoma.

Figure 3.  Popcorn calcification in pulmonary hamartoma. A magnified view of the right lower lobe from a CT scan shows a smoothly marginated nodule with several coarse foci of calcification (popcorn calcification). Also note the presence of foci of fat attenuation (arrows). The findings are virtually pathognomonic of hamartoma.

Figure 4.  Nodule with mixed attenuation. A magnified view of the right lung from a high-resolution CT scan shows a nodule with a predominantly solid component and a halo of groundglass attenuation (CT halo sign) (arrow) in a patient with invasive pulmonary adenocarcinoma.

32     Solitary Lung Nodule

n F  alse-negative

FDG-PET studies can be seen with carcinoid tumor, bronchioloalveolar carcinoma, and pulmonary carcinoma 3 cm in diameter and may be central or eccentric and 1-10 cm in diameter. n C  avity wall is usually thick in acute lung abscess, primary and metastatic carcinoma, and Wegener granulomatosis. n C  avity wall is usually thin in coccidioidomycosis, bronchogenic cyst, and traumatic pneumatocele.

Utility

n U  sually

first imaging modality used in the assessment of these patients.

CT

Findings

lung nodule or mass or poorly defined outer margins n T  hin-walled (3 cm in diameter. n C  avitation is seen in squamous cell carcinomas, large cell carcinomas, and adenocarcinomas, but not in small cell carcinomas. n C  ommon predisposing factors for lung abscess are alcoholism, anesthesia, trauma, and drug abuse.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n I n

majority of cases a cavity is evident on the radiograph. is superior to radiography in demonstrating presence of cavitation and associated findings. n N  eedle aspiration or biopsy is often helpful in establishing tissue diagnosis. n C  T

36

NODULES AND MASSES

Figure 1.  Chronic coccidioidomycosis. A 33-year-old man with a chronic productive cough developed acute chest pain while on vacation in Arizona. Chest radiograph showed a 3.3-cm subtle thin-walled cavity (arrows) in the right upper lobe. Cultures from sputum and bronchial washings grew Coccidioides immitis.

Solitary Cavitary Lung Nodule    37

Figure 2.  Chronic coccidioidomycosis. A 33-year-old man with chronic productive cough developed acute chest pain while on vacation in Arizona. CT scan confirmed a 3.3-cm thin-walled cavity in the right upper lobe. Cultures from sputum and bronchial washings grew Coccidioides immitis.

Suggested Readings Chong S, Lee KS, Yi CA, et al: Pulmonary fungal infection: Imaging findings in immunocompetent and immunocompromised patients. Eur J Radiol 59:371-383, 2006. Franquet T, Müller NL, Giménez A, et al: Spectrum of pulmonary aspergillosis: Histologic, clinical, and radiologic findings. RadioGraphics 21:825-837, 2001. Mueller PR, Berlin L: Complications of lung abscess aspiration and drainage. AJR Am J Roentgenol 178:1083-1086, 2002.

Ryu JH, Swensen SJ: Cystic and cavitary lung diseases: Focal and diffuse. Mayo Clin Proc 78:744-752, 2003. Seo JB, Im JG, Goo JM, et al: Atypical pulmonary metastases: Spectrum of radiologic findings. RadioGraphics 21:403-417, 2001. Woodring JH, Fried AM, Chuang VP: Solitary cavities of the lung: Diagnostic implications of cavity wall thickness. AJR Am J Roentgenol 135:1269-1271, 1980.

Multiple Lung Nodules DEFINITION: Presence of multiple nodules ≥1 cm in diameter.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  ulmonary

Findings

n P  ulmonary

metastases are evident as numerous bilateral nodules and masses of various sizes. n H  alo of ground-glass attenuation surrounding ­nodules (CT halo sign) is commonly seen in highly ­vascular or hemorrhagic tumors (angiosarcoma) and also in metastatic mucinous colon carcinoma, angioinvasive aspergillosis, and Wegener ­granulomatosis. n W  egener granulomatosis typically presents as ­multiple nodules and masses ranging from few mm up to 10 cm in diameter that often cavitate and have no lung zone predilection.

metastases: multiple nodules tend to be most numerous in the basal portions of the lungs, range in size from barely visible to large masses, and may be solid or cavitated. n T  uberculosis: nodules in endobronchial spread tend to measure 4-10 mm in diameter and to have a patchy distribution, whereas those of miliary tuberculosis measure 1-3 mm in diameter and are diffuse. n H  istoplasmosis and coccidioidomycosis usually pre­ sent as a single nodule measuring up to 3 cm in diameter or as multiple nodules 3 cm in diameter. n S  olitary masses: most commonly due to pulmonary carcinoma, lung abscess, post-traumatic lung cyst/hematoma. n L  arge pulmonary carcinomas that may cavitate or contain foci of calcification. n H  omogeneous water density in hydatid cyst and 50% of bronchogenic cysts. n I f located within a cavity, most commonly an aspergilloma. n M  ultiple masses: most commonly metastases or Wegener granulomatosis. n C  avitating metastases: most commonly due to squamous cell carcinoma but may also be seen in other tumors. Utility

n S  uperior

to the radiograph in demonstrating the presence of calcification and cavitation and associated findings such as lymphadenopathy.

MRI

Findings

n B  ronchogenic

cyst: almost all have homogeneous high signal intensity on T2-weighted images.

Utility

n H  elpful

in distinction of cystic from solid masses

DIFFERENTIAL DIAGNOSIS n P  ulmonary

carcinoma metastases n W  egener granulomatosis n L  ung abscess n P  ulmonary

are more likely than nodules to be ­malignant. diseases are characteristically solitary (e.g., primary pulmonary carcinoma, acute lung abscess, post-traumatic lung cyst). n O  ther diseases are characteristically multiple (e.g., metastatic carcinoma, Wegener granulomatosis, ­septic emboli, Churg-Strauss syndrome) n S  ome

n H  ydatid

cyst

n B  ronchogenic

cyst

PATHOLOGY n C  alcifications

are related to psammoma bodies, dystrophic calcification of necrotic carcinoma, incorporation of focus of previous granulomatous inflammation, or calcified bronchial cartilage within tumor. n C  avities are formed by necrosis of central portion of lesion and drainage of resultant partially liquefied material via communicating airways.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  ulmonary

mass has approximately 95% likelihood of being malignant. n I ncidence of cavitation in pulmonary carcinoma is about 10%. n M  ost common histologic type with cavitation is squamous cell carcinoma (22%). n T  hin-walled cavitated lesions are more likely to be benign; thick-walled (>15 mm) cavitated lesions are more likely malignant. n S  ingle lung metastases may occur particularly in testicular tumors and sarcomas.

Suggested Readings Aquino SL: Imaging of metastatic disease to the thorax. Radiol Clin North Am 43(3):481-495, 2005:vii. Lee KS, Kim TS, Fujimoto K, et al: Thoracic manifestation of Wegener’s granulomatosis: CT findings in 30 patients. Eur Radiol 13(1):43-51, 2003. Zylak CJ, Eyler WR, Spizarny DL, Stone CH: Developmental lung anomalies in the adult: Radiologic-pathologic correlation. RadioGraphics 22:S25-S43, 2002.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n Masses

are more likely than nodules to be malignant. of differential diagnosis falls into any one of the following groups: malignant neoplasm, infectious granulomas, benign tumors. n Calcification in mass does not exclude malignancy. n Majority

42

NODULES AND MASSES

Figure 1.  Pulmonary carcinoma. Posteroanterior chest radiograph shows large mass in the right lower lobe. The patient was a 73-year-old woman with pulmonary carcinoma.

Single and Multiple Pulmonary Masses    43

Figure 2.  Cavitation in pulmonary carcinoma. View of the right lung from a high-resolution CT shows right lower lobe mass with cavitation. The wall of the cavity is thick and has a nodular appearance. The patient was a 73-year-old man with pulmonary squamous cell carcinoma.

Figure 4.  Hydatid cyst. CT image shows homogeneous, water-density, thin-walled cyst in the left lung. The patient was a 51-year-old man with hydatid cyst due to Echinococcus granulosus.

Figure 3.  Calcification in carcinoma. CT image demonstrates foci of amorphous calcification within lobulated mass in a patient with metastatic adenocarcinoma of the colon.

Intracavitary Mass (Meniscus or Air Crescent Sign) DEFINITION: A crescent-shaped area of air surrounding round or oval opacity within a cavity on CT

and radiography.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  eniscus

Findings

n C  rescent-shaped

area of lucency within a cavity, nodule, mass, or consolidation (air crescent sign or meniscus sign).

Utility

n O  ften

first and only imaging modality used to make diagnosis.

CT

or air crescent sign surrounds an i­ntracavitary mass. n T  his sign is commonly seen in aspergilloma and angioinvasive aspergillosis and also may be occasionally seen in necrotizing pneumonia and ruptured hydatid cyst.

Findings

n O  ccasionally

Utility

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

n C  rescent-shaped

area of air density surrounding round or oval opacity within cavity (air crescent sign or meniscus sign).

n S  uperior

to radiography in demonstrating cavitation and air crescent sign.

CLINICAL PRESENTATION n H  emoptysis,

fever, cough

PATHOLOGY n A  spergilloma

(fungus ball) is a conglomeration of intertwined fungal hyphae admixed with mucus and cellular debris within a pulmonary cavity or ectatic bronchus. n C  avitating nodule, mass, or consolidation may be seen after angioinvasive fungal infection (Aspergillus, Mucor). n A  ngioinvasion leads to infarction; retraction of infarcted center and reabsorption of peripheral necrotic tissue results in air crescent between devitalized tissue and surrounding parenchyma.

this sign may be seen in necrotizing pneumonia and after rupture of hydatid cyst.

n V  ast

majority of cases are related to Aspergillus fumigatus. n A  spergilloma (fungus ball) with air crescent sign is seen most commonly in patients with upper lobe bronchiectasis or cavitation due to previous tuberculosis or long-standing sarcoidosis. n A  ngioinvasive aspergillosis is seen most commonly in immunocompromised patients with severe ­neutropenia. n N  ecrotizing pneumonia and ruptured hydatid cyst are uncommon causes of air crescent sign.

Suggested Readings Abramson S: The air crescent sign. Radiology 218:230-232, 2001. Franquet T, Müller NL, Giménez A, et al: Spectrum of pulmonary aspergillosis: Histologic, clinical, and radiologic findings. RadioGraphics 21:825-837, 2001. Jamadar DA, Kazerooni EA, Daly BD, et al: Pulmonary zygomycosis: CT appearance. J Comput Assist Tomogr 19:733-738, 1995. Koul PA, Koul AN, Wahid A, Mir FA: CT in pulmonary hydatid disease: Unusual appearances. Chest 118:1645-1647, 2000.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n Air

crescent sign results most commonly from aspergilloma (fungus ball) within pulmonary cavity or ectatic ­ ronchus or from angioinvasive aspergillosis in patients with severe neutropenia. b n CT is imaging modality of choice in diagnosis of aspergilloma and angioinvasive aspergillosis.

44

NODULES AND MASSES

Intracavitary Mass (Meniscus or Air Crescent Sign)    45

Figure 2.  Aspergilloma in tuberculous cavity. High-resolution CT image demonstrates large cavity in the left upper lobe containing homogeneous soft tissue mass (asterisk). The mass lies in the dependent portion of the cavity, suggesting that it is mobile. The findings are characteristic of intracavitary fungus ball. Note bilateral centrilobular emphysema and areas of scarring and bronchiectasis in the left upper lobe and extensive pleural thickening adjacent to the cavity. Figure 1.  Aspergilloma in tuberculous cavity. Magnified view of the left upper lobe from a frontal chest radiograph shows air crescent (arrows) surrounding an intracavitary mass. Also noted is bronchiectasis.

Figure 3.  Aspergilloma in tuberculous cavity. Coronal reformatted image better shows the intracavitary aspergilloma (asterisk) in the left upper lobe. Also noted is subpleural honey­combing in the lower lobes consistent with idiopathic pulmonary fibrosis. The patient was a 58-year-old man with previous tuberculosis and intracavitary aspergilloma.

Part 4 

INTERSTITIAL PATTERNS

Small Nodular Pattern DEFINITION: A small nodular pattern occurs with evidence of numerous round opacities 30 pack-years

DIFFERENTIAL DIAGNOSIS n N  onspecific

interstitial pneumonia pneumonitis n R  espiratory bronchiolitis/interstitial lung disease n D  esquamative interstitial pneumonia n L  ymphoid interstitial pneumonia n B  ronchioloalveolar carcinoma n H  ypersensitivity

PATHOLOGY n N  onspecific

interstitial pneumonia: alveolar wall inflammation and fibrosis n N  onspecific interstitial pneumonia: idiopathic or secondary to collagen vascular disease, drug reaction, or hypersensitivity pneumonitis n D  esquamative interstitial pneumonia: filling of alveolar airspaces with macrophages, mild alveolar wall inflammation, and mild fibrosis

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n G  round-glass

pattern is a common pattern of abnormality seen on high-resolution CT. chronic conditions associated with a ground-glass pattern include hypersensitivity pneumonitis and nonspecific interstitial pneumonia. n C  hest radiograph is normal in 10% of patients with interstitial lung disease. n C  ommon

64

INTERSTITIAL PATTERNS

Ground-Glass Pattern: Chronic Lung Disease    65

Figure 1.  Hypersensitivity pneumonitis. Chest radiograph shows hazy increased opacity (ground-glass opacity) in the middle and lower lung zones and poorly defined nodular opacities. The patient was a 42-year-old man with hypersensitivity pneumonitis.

Figure 2.  Ground-glass pattern. Maximum intensity projection image of the left lung illustrates characteristic appearance of ­ground-glass opacity with homogeneous increase in attenuation that does not result in obscuration of underlying vessels.

Figure 4.  Nonspecific interstitial pneumonia. High-resolution CT at the level of the lung bases shows extensive bilateral ­ ground-glass opacities. The patient was a 62-year-old man with nonspecific interstitial pneumonia. Figure 3.  Hypersensitivity pneumonitis. High-resolution CT image shows extensive bilateral ground-glass opacities, a few centrilobular nodules, and lobular areas of decreased attenuation and vascularity (arrows). The patient was a 65-year-old woman with subacute hypersensitivity pneumonitis.

66    Ground-Glass Pattern: Chronic Lung Disease

n R  espiratory

bronchiolitis/interstitial lung disease: smoking-related interstitial lung disease n L  ymphoid interstitial pneumonia: benign lymphoproliferative disorder in immunologic disorders (Sjögren syndrome) n H  ypersensitivity pneumonitis: alveolitis, bronchiolitis, ill-defined granulomas

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n H  ypersensitivity

pneumonitis is most common cause in normal hosts. n R  espiratory bronchiolitis/interstitial lung disease and desquamative interstitial pneumonia usually occur in smokers. n D  esquamative interstitial pneumonia and lymphoid interstitial pneumonia are uncommon conditions.

INTERSTITIAL PATTERNS

Suggested Readings Collins J, Stern EJ: Ground-glass opacity at CT: The ABCs. AJR Am J Roentgenol 169(2):355-367, 1997. Leung AN, Miller RR, Müller NL: Parenchymal opacification in ­chronic infiltrative lung diseases: CT-pathologic correlation. Radiology 188:209-214, 1993. Lynch DA, Travis WD, Müller NL, et al: Idiopathic interstitial pneumonias: CT features. Radiology 236(1):10-21, 2005. Nowers K, Rasband JD, Berges G, Gosselin M: Approach to groundglass opacification of the lung. Semin Ultrasound CT MR 23(4):302-323, 2002. Park CM, Goo JM, Lee HJ, et al: Nodular ground-glass opacity at thin-section CT: Histologic correlation and evaluation of change at follow-up. RadioGraphics 27(2):391-408, 2007. Silva CIS, Müller NL, Churg A: Hypersensitivity pneumonitis: Spectrum of high-resolution CT and pathologic findings. AJR Am J Roentgenol 188:334-344, 2007.

“Crazy-Paving” Pattern DEFINITION: Ground-glass opacities with superimposed septal lines and intralobular lines comprise the “crazy-paving” pattern. IMAGING

DIAGNOSTIC PEARLS

CT

n A  cute:

Findings

n B  ilateral

ground-glass opacities with superimposed smooth septal lines and intralobular lines

Utility

n N  onspecific

high-resolution CT pattern seen in a number of acute and chronic interstitial and airspace lung diseases

CLINICAL PRESENTATION n C  ough,

dyspnea in patients with “crazy-paving” pattern due to pulmonary hemorrhage n S  ymptoms either acute or chronic depending on cause of “crazy-paving” pattern n H  emoptysis

DIFFERENTIAL DIAGNOSIS n P  ulmonary

alveolar proteinosis interstitial pneumonia n A  cute respiratory distress syndrome n P  neumocystis pneumonia n L  ipoid pneumonia n B  ronchioloalveolar cell carcinoma n H  ydrostatic pulmonary edema n R  adiation-induced lung disease n C  hurg-Strauss syndrome n D  iffuse pulmonary hemorrhage n A  cute

PATHOLOGY n A  cute

conditions: acute respiratory distress syndrome, acute interstitial pneumonia, pulmonary edema, pulmonary hemorrhage, bacterial pneumonia, Pneumocystis

Pneumocystis pneumonia, acute respiratory distress syndrome, pulmonary hemorrhage n C  hronic: Pulmonary alveolar proteinosis, lipoid pneumonia, Churg-Strauss syndrome, bronchioloalveolar cell carcinoma pneumonia, Mycoplasma pneumonia, acute eosinophilic pneumonia n S  ubacute and chronic conditions: radiation pneumonitis, lipoid pneumonia, alveolar proteinosis, ChurgStrauss syndrome, bronchioloalveolar cell carcinoma

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n “  Crazy-paving”:

common pattern seen on high-resolution CT n A  cute causes: acute respiratory distress syndrome, acute interstitial pneumonia, pulmonary edema, pulmonary hemorrhage, bacterial pneumonia, Pneumocystis pneumonia, Mycoplasma pneumonia, acute eosinophilic pneumonia n S  ubacute or chronic causes: radiation pneumonitis, lipoid pneumonia, alveolar proteinosis, Churg-Strauss syndrome, bronchioloalveolar carcinoma

Suggested Readings Chung MJ, Lee KS, Franquet T, et al: Metabolic lung disease: Imaging and histopathologic findings. Eur J Radiol 54(2):233-245, 2005. Franquet T, Giménez A, Bordes R, et al: The crazy-paving pattern in exogenous lipoid pneumonia: CT-pathologic correlation. AJR Am J Roentgenol 170:315-317, 1998. Johkoh T, Itoh H, Müller NL, et al: Crazy-paving appearance at thinsection CT: Spectrum of disease and pathologic findings. Radiology 211:155-160, 1999. Murayama S, Murakami J, Yabuuchi H, et al: Crazy paving appearance” on high resolution CT in various diseases. J Comput Assist Tomogr 23:749-752, 1999.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n “  Crazy-paving”

is a high-resolution CT pattern characterized by smooth interlobular septal thickening and intralobular lines superimposed on ground-glass opacities. n M  any common acute and chronic interstitial and airspace diseases may result in a “crazy-paving” pattern. n D  ifferential diagnosis is based on presence of associated findings and clinical history. n D  efinitive diagnosis often requires lung biopsy.

70

INTERSTITIAL PATTERNS

“Crazy-Paving” Pattern    71

Figure 1.  “Crazy-paving” pattern in alveolar proteinosis. High-resolution CT image demonstrates bilateral ground-glass opacities with superimposed smooth septal lines and intralobular lines resulting in a pattern known as “crazy-paving.” The patient was a 45-year-old man with alveolar proteinosis.

Figure 2.  “Crazy-paving” pattern acute respiratory distress syndrome. High-resolution CT image shows bilateral ground-glass opacities and areas of consolidation involving mainly the dependent lung regions. Smooth septal lines and intralobular lines are present in the areas of ground-glass opacity (“crazy-paving” pattern). The patient was a 70-year-old man with acute respiratory distress syndrome.

Part 5 

DECREASED LUNG DENSITY

Mosaic Perfusion Pattern DEFINITION: Areas with decreased attenuation and vascularity with blood flow redistribution to normal lung result in areas of increased attenuation and vascularity called a mosaic perfusion pattern. IMAGING

DIAGNOSTIC PEARLS

CT

n M  osaic

Findings n A  reas

of decreased attenuation and vascularity with blood flow redistribution to normal lung results in the so-called mosaic perfusion pattern on inspiratory CT. n M  osaic perfusion pattern is seen most commonly in patients with obliterative bronchiolitis and asthma or chronic thromboembolic pulmonary arterial hypertension. n H  igh-resolution CT findings of asthma include thickening and narrowing of bronchi, bronchial dilatation, patchy areas of decreased attenuation and vascularity on inspiratory images, and air trapping on expiratory CT. n O  bliterative bronchiolitis (bronchiolitis obliterans) is shown by areas of decreased attenuation and vascularity on inspiratory CT scans and air trapping on expiratory scans; bronchiectasis is commonly present. n C  hronic pulmonary thromboembolic pulmonary arterial hypertension results in a mosaic perfusion pattern and increased diameter of the main, lobar, and segmental pulmonary arteries. n C  ontrast-enhanced CT shows eccentric flattened mural thrombi that may be occlusive or have areas of recanalization; chronically occluded vessels are typically smaller than expected. Utility n C  T

is seldom indicated in patients with asthma. n C  T is the imaging modality of choice in the diagnosis of obliterative bronchiolitis. n C  ontrast-enhanced CT is the imaging modality of choice in the diagnosis of chronic pulmonary thromboembolism.

CLINICAL PRESENTATION n P  rogressive

shortness of breath and cough in asthma n P  ulmonary arterial hypertension in chronic pulmonary embolism n W  heezing

attenuation pattern may be due to mosaic perfusion or patchy ground-glass opacities n M  osaic attenuation due to patchy ground-glass typically has similar size vessels in the areas of groundglass as in the adjacent uninvolved parenchyma n P  ulmonary vessels in areas of apparent groundglass opacity due to mosaic perfusion are typically larger and more numerous than in the adjacent parenchyma

PATHOLOGY n O  ligemia

secondary to decreased vascularity may result from partial airway obstruction (asthma, obliterative bronchiolitis) or obliteration of small peripheral vessels (emphysema) and vascular obstruction (pulmonary thromboembolism). n B  lood flow redistribution to normal lung results in areas of increased attenuation and vascularity.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  osaic

perfusion pattern is a common manifestation of obliterative bronchiolitis n C  ommonly seen in chronic thromboembolic pulmonary arterial hypertension

Suggested Readings King MA, Ysrael M, Bergin CJ: Chronic thromboembolic pulmonary hypertension: CT findings. AJR Am J Roentgenol 170:955-960, 1998. Oikonomou A, Dennie CJ, Muller NL, et al: Chronic thromboembolic pulmonary arterial hypertension: Correlation of postoperative results of thromboendarterectomy with preoperative helical contrast-enhanced computed tomography. J Thorac Imaging 19:6773, 2004. Pipavath SJ, Lynch DA, Cool C, et al: Radiologic and pathologic features of bronchiolitis. AJR Am J Roentgenol 185:354-363, 2005.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n M  osaic

perfusion pattern is a common manifestation of obliterative bronchiolitis. patients with pulmonary hypertension, presence of mosaic perfusion pattern on CT is highly ­ suggestive of chronic pulmonary thromboembolism.

n I n

72

DECREASED LUNG DENSITY

Figure 1.  Mosaic perfusion pattern in asthma. High-resolution CT performed at end inspiration shows extensive bilateral areas of decreased attenuation and vascularity with blood flow redistribution to normal lung resulting in a mosaic perfusion pattern. The patient was a 54-year-old woman with severe chronic asthma.

Figure 3.  Mosaic perfusion in chronic thromboembolic pulmonary hypertension. High-resolution CT image at the level of the upper lobes shows areas with decreased attenuation and vascularity (straight arrows) and areas with increased attenuation and vascularity (mosaic perfusion pattern). Note the marked enlargement of the pulmonary arteries as compared with the normal-sized bronchi. The patient was a 57-year-old woman with chronic thromboembolic pulmonary hypertension.

Silva CI, Colby TV, Müller NL: Asthma and associated conditions: High-resolution CT and pathologic findings. AJR Am J Roentgenol 183:817-824, 2004. Visscher DW, Myers JL: Bronchiolitis: The pathologist’s perspective. Proc Am Thorac Soc 3:41-47, 2006.

Mosaic Perfusion Pattern    73

Figure 2.  Obliterative bronchiolitis. High-resolution CT images shows decreased attenuation and vascularity in most of the left lung, anterior aspect of the right upper lobe, and superior segment of the right lower lobe. Also noted is bronchiectasis (arrows). The findings are characteristic of bronchiolitis obliterans. The uninvolved portions of the right upper lobe have increased vascularity and attenuation due to blood flow redistribution. The patient was a 69-year-old woman with obliterative bronchiolitis associated with rheumatoid arthritis.

Figure 4.  Mosaic perfusion in chronic thromboembolic pulmonary hypertension. CT pulmonary angiogram demonstrates eccentric filling defect in the left pulmonary artery (curved arrow) and irregular arterial lumen consistent with chronic pulmonary thromboembolism. The patient was a 57-year-old woman.

Worthy SA, Müller NL, Hartman TE, et al: Mosaic attenuation pattern on thin-section CT scans of the lung: Differentiation among infiltrative lung, airway, and vascular diseases as a cause. Radiology 205:465-470, 2005.

Air Trapping DEFINITION: Air trapping refers to obstruction of the egress of air from affected lung parenchyma. IMAGING

DIAGNOSTIC PEARLS

Radiography

n U  nilateral:

Findings

n I nspiratory

radiograph is frequently normal or may show increased radiolucency and decreased vascularity; hyperinflation may be seen in severe cases. n M  ost common radiographic abnormalities in patients who have asthma are hyperinflation and bronchial wall thickening. n O  bliterative bronchiolitis (bronchiolitis obliterans) may be associated with increased lung volumes and peripheral attenuation of vascular markings. n U  nilateral or lobar air trapping on expiratory radiograph and normal or decreased ipsilateral lung volume on inspiratory radiograph may be seen in SwyerJames-McLeod syndrome and endobronchial tumor. n F  ocal hyperlucency on inspiratory radiograph and air trapping on expiratory radiograph are typical findings of congenital lobar emphysema and bronchial atresia. Utility

n I nspiratory n E  xpiratory

trapping.

radiograph is frequently normal. radiograph is required to demonstrate air

endobronchial tumor, foreign body, Swyer-James-McLeod syndrome, bronchial atresia, congenital lobar emphysema n B  ilateral: bronchiolitis obliterans, asthma, normal (most commonly left upper lobe), and air trapping on expiratory scans. n B  ronchial atresia: increased volume, decreased attenuation and vascularity of involved pulmonary segment, and air trapping on expiratory scans. n B  ronchial atresia: bronchial dilatation immediately distal to atresia, mucoid impaction within ectatic bronchus (bronchocele), and occlusion of bronchus central to bronchocele. Utility

n E  xpiratory

high-resolution CT is superior to radiography in demonstrating focal and diffuse areas of air trapping. n C  T findings are usually diagnostic in patients with endobronchial tumors, Swyer-James-McLeod syndrome, congenital lobar emphysema, and bronchial atresia.

CLINICAL PRESENTATION

CT

Findings n N  ormal

subjects: mild air trapping common, typically limited to dependent lung regions and the tip of the middle lobe and lingula area, and involves less than 25% of lung parenchyma. n A  sthma: thickening and narrowing of bronchi, bronchial dilatation, patchy areas of decreased attenuation, and vascularity (mosaic perfusion pattern) on inspiratory images and air trapping on expiratory CT. n O  bliterative bronchiolitis (bronchiolitis obliterans): areas of decreased attenuation and vascularity (mosaic perfusion pattern) on inspiratory CT scans and air trapping on expiratory scans; bronchiectasis commonly present. n E  ndobronchial tumor and Swyer-James-McLeod syndrome: decreased attenuation and vascularity of affected lung on inspiration and air trapping on expiration; normal or decreased volume of affected lobe or lung in adults. n C  ongenital lobar emphysema: increased volume, decreased attenuation and vascularity of involved lobe

n P  atients

commonly asymptomatic shortness of breath and cough n W  heezing in asthma and central endobronchial tumors n P  rogressive

DIFFERENTIAL DIAGNOSIS n O  bliterative n A  sthma

bronchiolitis (bronchiolitis obliterans)

n S  wyer-James-McLeod

syndrome tumor n E  ndobronchial foreign body n N  ormal (when mild and limited to certain regions) n E  ndobronchial

PATHOLOGY n A  ir

trapping results from obstruction of egress of air from affected lung parenchyma. n V  olume of lung behind a partly obstructing endobronchial lesion is almost invariably reduced at total lung capacity.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n W  heezing

may result from asthma or partial central bronchial obstruction by tumor or foreign body. and expiratory high-resolution CT is the imaging modality of choice in the diagnosis of air trapping in patients with suspected obliterative bronchiolitis. n CT is seldom indicated in patients with asthma. n CT findings are usually diagnostic in patients with endobronchial tumors, Swyer-James-McLeod syndrome, congenital lobar emphysema, and bronchial atresia. n Inspiratory

74

Air Trapping    75

DECREASED LUNG DENSITY

Figure 1.  Air trapping due to endobronchial tumor. Expiratory chest radiograph shows air trapping of the right lung with contralateral shift of the mediastinum. The patient was a 31-yearold woman with partial obstruction of the right main-stem bronchus by an endobronchial carcinoid.

Figure 3.  Swyer-James-McLeod syndrome. Inspiratory highresolution CT image shows decreased attenuation and vascularity of the left lung with associated bronchiectasis and mild volume loss leading to ipsilateral shift of the mediastinum and anterior junction line. The patient was a 61-year-old woman with SwyerJames-McLeod syndrome.

n D  ensity

of affected parenchyma is less than that of opposite lung from decreased perfusion (oligemia) secondary to hypoventilation-mediated hypoxic vasoconstriction.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  ir

trapping is a characteristic feature of asthma, obliterative bronchiolitis (bronchiolitis obliterans), partial bronchial obstruction by foreign body or tumor, bronchial atresia, and congenital lobar emphysema.

Figure 2.  Air trapping in obliterative bronchiolitis. Expiratory high-resolution CT demonstrates extensive bilateral air trapping. The patient was a 54-year-old woman with obliterative bronchiolitis after stem cell transplantation for multiple myeloma.

Figure 4.  Swyer-James-McLeod syndrome. Expiratory highresolution CT image shows air trapping in the left lung. The mediastinum and anterior junction line are in the midline. The patient was a 61-year-old woman with Swyer-James-McLeod syndrome.

Suggested Readings Matsushima H, Takayanagi N, Satoh M, et al: Congenital bronchial atresia: Radiologic findings in nine patients. J Comput Assist Tomogr 26:860-864, 2002. Pipavath SJ, Lynch DA, Cool C, et al: Radiologic and pathologic features of bronchiolitis. AJR Am J Roentgenol 185:354-363, 2005. Silva CI, Colby TV, Müller NL: Asthma and associated conditions: High-resolution CT and pathologic findings. AJR Am J Roentgenol 183:817-824, 2004. Visscher DW, Myers JL: Bronchiolitis: The pathologist’s perspective. Proc Am Thorac Soc 3:41-47, 2006.

Unilateral Hyperlucent Lung DEFINITION: A hyperlucent lung is a lung that has increased lucency compared to the other lung on the chest radiograph or CT. IMAGING

DIAGNOSTIC PEARLS

Radiography

n A  ir

Findings

n S  wyer-James-McLeod

syndrome: hyperlucent lung or lobe, decreased vascularity, normal or reduced volume during inspiration, and air trapping during expiration. n P  artial bronchial obstruction (endobronchial tumor, bronchial stenosis). n N  onpulmonary causes of hyperlucent “lung” on chest radiograph: faulty technique (patient rotation), chest wall abnormalities (mastectomy, congenital absence of the pectoralis muscle (Poland syndrome), and pneumothorax. Utility

n D  iagnosis

of Swyer-James-McLeod syndrome often first suspected on chest radiograph in asymptomatic patient

CT

trapping on expiratory radiograph or CT: Swyer-James-McLeod syndrome, partial bronchial obstruction n N  o air trapping: proximal interruption or narrowing of the pulmonary artery n N  onpulmonary causes: mastectomy, absence of pectoralis muscles (Poland syndrome), patient rotation n T  ypically left upper lobe: congenital lobar ­emphysema, bronchial atresia

DIFFERENTIAL DIAGNOSIS n S  wyer-James-McLeod n E  ndobronchial n F  oreign

Findings

n S  wyer-James-McLeod

syndrome: decreased attenuation and vascularity of affected lung on inspiration, normal or reduced lung volume on inspiratory CT, air trapping on expiration, bronchiectasis. n P  artial bronchial obstruction (endobronchial tumor, bronchial stenosis). n A  symmetric emphysema. n E  xtensive unilateral or asymmetric pulmonary embolism. n L  obar collapse with compensatory overinflation of remaining lung. n P  revious lobectomy or bilobectomy. n U  nilateral lung transplant for emphysema. Utility n C  T

is superior to radiography in diagnosis of unilateral hyperlucent lung and underlying cause. n I nspiratory and expiratory high-resolution CT is the best imaging technique for assessment of patients with suspected bronchiolitis obliterans or Swyer-JamesMcLeod syndrome.

body

tumor

syndrome

n A  telectasis

n P  neumothorax n M  astectomy n P  oland

n P  atient

syndrome rotation

PATHOLOGY n S  wyer-James-McLeod

syndrome: decreased lung density results from reduction in quantity of blood due to bronchiolitis obliterans in absence of pulmonary overinflation; it most commonly results as a sequela of childhood respiratory infections, most often viral. n O  ther causes of unilateral hyperlucent lung include partial endobronchial obstruction, asymmetric emphysema, and unilateral or asymmetric pulmonary embolism.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  ommon

CLINICAL PRESENTATION n P  atients n C  ough,

are often asymptomatic. dyspnea

cause of hyperlucent lung is partial endobronchial obstruction by tumor or foreign body. n S  wyer-James-McLeod or unilateral hyperlucent lung syndrome is an uncommon condition that typically is a sequela of childhood viral or Mycoplasma infection.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n U  nilateral

hyperlucency on the radiograph may also result from pneumothorax and congenital and acquired abnormalities of the chest wall. n Chest wall abnormalities, in particular mastectomy, are the most common cause of unilateral hyperlucent “lung” on radiography. n Common cause of hyperlucent lung is partial endobronchial obstruction by tumor or foreign body. n CT is superior to radiography in diagnosis of unilateral hyperlucent lung and the underlying cause.

76

DECREASED LUNG DENSITY

Figure 1.  Swyer-James-McLeod syndrome. Chest radiograph shows hyperlucency and decreased vascularity of the left lung. The mediastinum is shifted to the left consistent with decreased left lung volume. The patient was a 40-year-old man.

Figure 3.  Unilateral hyperlucent lung due to central carcinoid tumor. Posteroanterior chest radiograph demonstrates a tumor in the right main bronchus (arrows). The right lung is slightly smaller than the left and shows decreased vascularity. The patient was a 48-year-old woman with a diagnosis of typical carcinoid tumor made at bronchoscopy and confirmed at surgery.

Unilateral Hyperlucent Lung    77

Figure 2.  Unilateral hyperlucency secondary to left mastectomy. Posteroanterior chest radiograph shows increased lucency of the left hemithorax. The patient was a 74-year-old woman.

Figure 4.  Unilateral hyperlucent lung. Inspiratory highresolution CT image shows endoluminal tumor in right main bronchus. Note decreased size of right lung and diffuse decrease in attenuation and vascularity as compared with the left lung. The patient was a 31-year-old woman with a typical carcinoid tumor. She presented with recurrent episodes of shortness of breath and tightness in the chest and had a clinical diagnosis of asthma.

Suggested Readings Jeung MY, Gasser B, Gangi A, et al: Bronchial carcinoid tumors of the thorax: Spectrum of radiologic findings. RadioGraphics 22:351-365, 2002. Lucaya J, Gartner S, Garcia-Pena P, et al: Spectrum of manifestations of Swyer-James-MacLeod syndrome. J Comput Assist Tomogr 22:592-597, 1998.

Moore ADA, Godwin JD, Dietrich PA, et al: Swyer-James syndrome: CT findings in eight patients. AJR Am J Roentgenol 158:1211-1215, 1992.

Bilateral Hyperlucent Lungs DEFINITION: Increased lucency of both lungs results from generalized excess air or alteration in pulmonary vasculature. IMAGING

DIAGNOSTIC PEARLS

Radiography

n E  mphysema:

Findings

n E  mphysema:

overinflation with diaphragm depressed often to level of 7th rib anteriorly, 11th interspace, or 12th rib posteriorly. n D  istance >2.5 cm between posterior sternum and most anterior margin of ascending aorta indicative of overinflation. n E  mphysema: irregular areas of radiolucency, local avascular areas, distortion of vessels, bullae, and hyperinflation. n O  verinflation shown by dome of diaphragm located 2.5 cm distance between the posterior sternum and the most anterior margin of the ascending aorta) and flattening of the diaphragm. The patient was a 52-year-old man with severe panacinar emphysema due to α1-antitrypsin deficiency. Hoffman EA, Simon BA, McLennan G: State of the art: A structural and functional assessment of the lung via multidetector-row ­computed tomography: Phenotyping chronic obstructive pulmonary disease. Proc Am Thorac Soc 3:519-532, 2006. Kilburn KH, Warshaw RH, Thornton JC: Do radiographic criteria for emphysema predict physiologic impairment? Chest 107:1225-1231, 1995.

Bilateral Hyperlucent Lungs    79

Figure 2.  Centrilobular and paraseptal emphysema. Posteroanterior chest radiograph shows increased lung volumes, slight distortion of the upper lobe vessels, and focal areas of lucency in the upper lobes. The patient was a 53-year-old smoker.

Figure 4.  Postinfectious obliterative bronchiolitis. Highresolution CT image at the level of left main bronchus shows extensive bilateral areas of decreased attenuation and vascularity with blood flow redistribution (mosaic perfusion pattern). The patient was a 24-year-old woman with obliterative bronchiolitis following severe viral infection when the patient was 9 months old.

Pratt PC: Role of conventional chest radiography in diagnosis and exclusion of emphysema. Am J Med 82:998-1006, 1987. Silva CI, Colby TV, Muller NL: Asthma and associated conditions: High-resolution CT and pathologic findings. AJR Am J Roentgenol 183:817-824, 2004. Thurlbeck WM, Müller NL: Emphysema: Definition, imaging, and quantification. AJR Am J Roentgenol 163:1017-1025, 1994.

Part 6 

 IRWAY AND PARENCHYMAL A ­ANOMALIES

Bronchial Atresia DEFINITION: Bronchial atresia is a rare congenital anomaly characterized by short-segment obliteration of a lobar, segmental, or subsegmental bronchus at or near its origin. IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  ucoid

Findings n A  rea

of pulmonary hyperlucency (90% of cases) nodule or mass (80%) n A  djacent normal lung compressed and displaced n M  ediastinal displacement: may or may not be evident n D  ecreased vascularity of affected segment n O  void, round, or branching opacities near hilum due to accumulation of secretions and mucoid impaction distal to bronchial atresia n A  ir trapping evident on expiratory chest radiographs n H  ilar

Utility

n R  adiographic

findings usually characteristic

CT

impaction, segmental hyperlucency, and decreased vascularity n A  ir trapping of affected segment and presence of hilar nodule or mass n M  ost commonly apico-posterior segment of left upper lobe but may affect any pulmonary segment

Utility n O  f

limited value in diagnosis

CLINICAL PRESENTATION n M  ajority

Findings n M  ucoid

impaction seen as presence of branching soft tissue densities in bronchial distribution, usually associated with bronchial dilatation. n B  ronchial occlusion and mucoid impaction with bronchial dilatation (bronchocele) immediately distal to atretic bronchus. n D  ecreased vascularity and attenuation and increased volume of affected segment. Utility

n M  ost

sensitive imaging technique for confirming ­diagnosis n I maging modality of choice n D  isorder best appreciated on multiplanar and volumetric reconstructions n E  xcellent visualization of mucoid impaction and segmental overinflation and hypovascularity

MRI

Findings n M  ucoid

impaction shown as variable signal intensity on T1-weighted images and typically very high signal intensity on T2-weighted images.

n S  ome

of cases are asymptomatic. patients present with recurrent pneumonia.

DIFFERENTIAL DIAGNOSIS n A  spiration

of foreign body tumor

n E  ndobronchial

PATHOLOGY n S  hort-segment

obliteration of lobar, segmental, or subsegmental bronchus occurs at or near its origin. n P  athogenesis of airway interruption is unknown; airway and airspaces distal to obstruction develop ­normally. n P  atent bronchial tree peripheral to point of obliteration results in accumulation of mucus and mucocele distal to atresia. n A  lveoli supplied by atretic bronchus are ventilated by collateral pathways, showing air trapping and resulting in hyperinflation. n H  yperlucency results from combination of oligemia and in­crease in the volume of air within the affected parenchyma.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n S  eldom

associated with significant complications and thus rarely requires surgical resection of affected segment or lobe. n C  T findings are usually diagnostic.

82

Bronchial Atresia    83

AIRWAY AND PARENCHYMAL ANOMALIES

Figure 1.  Bronchial atresia. Chest radiograph shows increased lucency in the left middle and upper lung zones. (Courtesy of Dr. Jim Barrie, University of Alberta Medical Center, Edmonton, Canada.)

Figure 2.  Bronchial atresia. CT scan demonstrates marked decrease in attenuation and vascularity of the superior segment of the left lower lobe. Also noted is anterior displacement of the left major fissure due to hyperinflation of the superior segment. An oval opacity is present posterior to the left hilum (arrow). This represents a bronchocele distal to the atretic superior segmental bronchus of the left lower lobe. (Courtesy of Dr. Jim Barrie, University of Alberta Medical Center, Edmonton, Canada.)

Figure 3.  Bronchial atresia. High-resolution CT image at the level of the thoracic inlet demonstrates decrease in attenuation and vascularity of the anterior segment of the left upper lobe. The patient was a 19-year-old woman. Figure 4.  Bronchial atresia. 3D external volume rendering image of central airways viewed from an anterior perspective shows atresia of right upper lobe bronchus. Also noted is abnormal branching pattern of the right middle lobe bronchus.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n R  are

congenital anomaly common in men n E  stimated prevalence: approximately 1 case per 100,000 population n M  ore

Suggested Readings Berrocal T, Madrid C, Novo S, et al: Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: Embryology, radiology, and pathology. RadioGraphics 24:17, 2004. Ghaye B, Szapiro D, Fanchamps JM, Dondelinger RF: Congenital bronchial abnormalities revisited. RadioGraphics 21:105-119, 2001. Jederlinic PJ, Sicilian LS, Baigelman W, Gaensler EA: Congenital bronchial atresia: A report of 4 cases and a review of the literature. Medicine (Baltimore) 66:73-83, 1987. Kinsella D, Sissons G, Williams MP: The radiological imaging of bronchial atresia. Br J Radiol 65:681-685, 1992.

Bronchogenic Cyst DEFINITION: Bronchogenic cysts are congenital cysts lined with bronchial epithelium that arise from abnormal separation of localized portions of the tracheobronchial tree from the adjacent airways. IMAGING

DIAGNOSTIC PEARLS

Radiography

n W  ater

Findings

n M  ediastinal

cysts: round, oval masses usually in right paratracheal or subcarinal region. n P  ulmonary cysts: sharply circumscribed, solitary, round or oval mass usually involving the medial third of lower lobe. n A  ir-containing cysts, with or without fluid when communication is established. Utility

n S  erial

radiographs: show little change in size and shape with time. n C  hest radiograph: initial imaging modality but does not allow confident diagnosis.

CT

Utility

n S  uperior

to CT in evaluation for suspected bronchogenic cysts; allows confident diagnosis in virtually 100% of cases. n L  ack of radiation exposure and higher specificity.

CLINICAL PRESENTATION n N  o

Findings

n H  omogeneous n M  ediastinal

vessel.

density on CT in approximately 50% high signal intensity on T2-weighted images n L  ack of enhancement after intravenous administration of contrast material on CT and MRI n H  omogeneous

cystic mass with thin smooth wall. cysts tend to mold to adjacent airway or

n P  ulmonary

cysts displace adjacent parenchyma. attenuation is at or near water density (−10 to +10 Hounsfield units in 50% of cases). n C  ysts are indistinguishable from soft tissue lesions in the other 50% of cases. n I nfected cysts have inhomogeneous enhancement and resemble abscess. n L  ung adjacent to cyst is frequently abnormal and shows areas of decreased attenuation and scarring. n H  omogeneous

Utility

n C  onfident

diagnosis can be made in approximately 50% of cases; remaining cysts have soft tissue attenuation due to protein content.

symptoms evident in majority of cases wheezing, stridor, and pneumonia due to compression of trachea or bronchi n D  ysphagia due to compression of esophagus n L  ocalized pulmonary edema due to compression of adjacent pulmonary vein n I nfection in approximately 20% of patients with intraparenchymal cysts n H  emoptysis and pneumothorax less common n C  ough,

DIFFERENTIAL DIAGNOSIS n C  ongenital

cystic adenomatoid malformation (congenital pulmonary airway malformation) n H  ydatid cyst n B  enign or malignant neoplasm n G  ranuloma

PATHOLOGY

MRI

Findings n C  yst

filled predominantly with water or serous fluid: low signal intensity on T1-weighted images. n C  yst with high protein content: high signal intensity. n H  omogeneous high-signal intensity on T2-weighted spin-echo images. n I nfected or hemorrhagic cyst: inhomogeneous and variable intensity on both T1- and T2-weighted images.

n A  bnormal

separation of localized portions of tracheobronchial tree from adjacent airways occurs between 3rd and 24th weeks of gestation. n B  ronchogenic cysts are thin-walled, unilocular, spherical, and either mucoid or serous filled. n C  yst wall is lined by respiratory epithelium and contains smooth muscle and commonly cartilage. n E  stablished communication with tracheobronchial tree is due to infection or instrumentation.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n C  T

allows confident diagnosis in 50% of cases. allows confident diagnosis in virtually 100% of cases. n CT-guided needle aspiration of cyst contents is confirmatory after inconclusive CT and MR diagnosis of cystic content. n MRI

84

Bronchogenic Cyst    85

AIRWAY AND PARENCHYMAL ANOMALIES

Figure 1.  Bronchogenic cyst. Magnified view from contrastenhanced CT scan shows a paratracheal mass (arrows) with homogeneous water density. The attenuation value of the mass was 9 Hounsfield units. The patient was a 58-year-old woman with a bronchogenic cyst.

Figure 3.  Pulmonary bronchogenic cyst. CT image photographed at mediastinal window setting shows that the nodule has soft tissue attenuation (arrow). The patient was a 41-year-old woman with a presumptive diagnosis of pulmonary bronchogenic cyst. n C  ommunication

between cyst and tracheobronchial tree can result in a check-valve mechanism and lead to rapid expansion of the cyst.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n B  ronchogenic

cysts are uncommon and usually isolated. n A  pproximately 75% of cysts are located in the mediastinum and 25% in the lung. n I nfection occurs in approximately 20% of patients with intraparenchymal cysts.

Figure 2.  Mediastinal bronchogenic cyst. Contrast mediumenhanced CT demonstrates a cystic mass in the subcarinal region (arrows). The patient was a 32-year-old woman with a bronchogenic cyst.

Figure 4.  Bronchogenic cyst. T2-weighted MR image demonstrates homogeneous high signal intensity similar to that of cerebrospinal fluid. The findings are characteristic of a bronchogenic cyst. The patient was a 72-year-old woman.

Suggested Readings Berrocal T, Madrid C, Novo S, et al: Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: Embryology, radiology, and pathology. RadioGraphics 24:e17, 2004. Mendelson DS, Rose JS, Efremidis SC, et al: Bronchogenic cysts with high CT numbers. AJR Am J Roentgenol 140:463-465, 1983. Naidich DP, Rumancik WM, Ettenger NA, et al: Congenital anomalies of the lungs in adults: MR diagnosis. AJR Am J Roentgenol 151:1319, 1988. Nakata H, Egashira K, Watanabe H, et al: MRI of bronchogenic cysts. J Comput Assist Tomogr 17:267-270, 1993. Suen HC, Mathisen DJ, Grillo HC, et al: Surgical management and radiological characteristics of bronchogenic cysts. Ann Thorac Surg 55:476-481, 1993. Yoon YC, Lee KS, Kim TS, et al: Intrapulmonary bronchogenic cyst: CT and pathologic findings in five adult patients. AJR Am J Roentgenol 179:167-170, 2002.

Congenital Cystic Adenomatoid Malformation (Congenital Pulmonary Airway Malformation) DEFINITION: Congenital cystic adenomatoid malformation is an abnormality characterized by a multicystic mass of pulmonary tissue with an abnormal proliferation of bronchial structures.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n R  adiographs

Findings

n U  nilocular

or multiloculated cyst soft tissue and cystic mass ranging from 4-12 cm in diameter n O  ccasional preferential expansion of one cyst, creating a single lucent area n S  pace-occupying lesion n C  omplex

Utility

n P  neumonia

in surrounding parenchyma results in obscuration of malformation or development of fluid levels. n R  adiographic findings are suggestive of the diagnosis.

CT

Findings

n U  nilocular

or multiloculated cyst soft tissue and cystic mass ranging from 4-12 cm in diameter n T  ype I: at least one cyst >2 cm in diameter n T  ype II: multiple thin-walled cysts ranging from 2-20 mm in diameter n C  omplex

Utility

n S  uperior

to chest radiography in demonstrating both cystic and solid components. n P  erformed almost routinely in adults with cystic lung lesions.

CLINICAL PRESENTATION n I ncreasing

respiratory distress in neonatal period adults, incidental finding or accompanied by symptoms of recurrent respiratory infections (cough and fever) n P  neumothorax (occasionally) n I n

DIFFERENTIAL DIAGNOSIS n B  ronchogenic n L  ung

abscess

cyst

usually show cystic mass most c­ ommonly in lower lobes. n C  T finding in adults typically consists of multiple thin-walled, complex cystic masses ranging from 4-12 cm in diameter.

n L  ung

tumor sequestration

n L  obar

PATHOLOGY n H  eterogeneous,

complex congenital malformation, typically cystic, containing smooth muscle but generally no cartilage n T  ype I: large, often multiloculated cysts of >2 cm in diameter n T  ype II: uniform small cysts of 14 days before initial symptoms. IMAGING

DIAGNOSTIC PEARLS

Radiography

n Lobar pneumonia: nonsegmental, homogeneous consolidation involving predominantly or exclusively one lobe with visible air bronchograms. n Bronchopneumonia: patchy areas of consolidation that may be lobular, subsegmental or segmental, although may coalesce to involve entire lobe. n Interstitial pneumonia: extensive peribronchial thickening and ill-defined reticulonodular opacities; associated patchy subsegmental/plate-like atelectasis/focal areas of consolidation. n C  hest radiograph plays major role in confirming presence of pneumonia but is of limited value in making a specific diagnosis.

Findings n L  obar

pneumonia: homogeneous airspace consolidation involving adjacent segments of lobe. n B  ronchopneumonia: patchy or confluent areas of consolidation involving one or more segments of single lobe or multiple lobes. n P  eribronchial thickening and ill-defined reticulonodular opacities with or without associated focal areas of consolidation in infectious bronchiolitis and early bronchopneumonia. n R  ound pneumonia: focal spherical area of consolidation. Utility

n A  ccording

to American Thoracic Society (ATS) guidelines, posteroanterior (and lateral when possible) chest radiography should be obtained whenever pneumonia is suspected in adults. n I nitial examination is usually sufficiently specific to preclude need for additional imaging. n F  indings are informative with regard to extent of ­pneumonia, presence of cavitation, associated conditions, pleural effusion, and alternative diagnosis.

CT

n B  ronchopneumonia:

lobular, subsegmental or segmental ground-glass opacities or areas of ­consolidation involving one or more segments of single lobe or multiple lobes. n C  entrilobular nodules and “tree-in-bud pattern” seen in infectious bronchiolitis due to viruses, Mycoplasma, bacteria, or fungi. Utility

n S  eldom

indicated in community-acquired pneumonia. in detection, differential diagnosis, and management of patients with pulmonary or pleural complications.

n H  elpful

Findings n L  obar

pneumonia: homogeneous airspace consolidation involving adjacent segments of a lobe. n B  ronchopneumonia (lobular pneumonia): centrilobular nodules and “tree-in-bud” pattern due to associated bronchiolitis; poorly defined focal nodular opacities measuring 5-10 mm in diameter (airspace nodules).

CLINICAL PRESENTATION n A  cute

respiratory symptoms (cough, sputum production, and/or dyspnea) accompanied by fever and auscultatory findings (abnormal breath sounds and crackles).

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n C  hest

radiography has pivotal role in confirming or excluding pneumonia but is of limited value in ­ etermining specific etiology of community-acquired pneumonia. d n I n the absence of clinical information, the radiologist cannot reliably distinguish between pneumonia and other pulmonary processes. n A  TS guidelines recommendation: posteroanterior (and lateral when possible) chest radiography be ­performed in all adults with clinically suspected pneumonia. n C  T seldom warranted in diagnosis of community-acquired pneumonia; main role is in evaluation of patients with suspected complications such as empyema or necrotizing pneumonia.

114

COMMUNITY ACQUIRED AND NOSOCOMIAL PNEUMONIA

Figure 1.  Lobar pneumonia. Chest radiograph in a 48-yearold man with clinical symptoms suggestive of pneumonia demonstrates lobar right upper lobe consolidation with air bronchograms and sharp demarcation by the minor fissure.

Figure 3.  Round pneumonia. Chest radiograph in a 56-year-old woman with proven pneumococcal pneumonia shows an area of homogeneous round consolidation in the left lung.

DIFFERENTIAL DIAGNOSIS n A  spiration

pneumonia pneumonia n C  hronic eosinophilic pneumonia n B  ronchioloalveolar cell carcinoma n P  ulmonary lymphoma n A  cute pulmonary embolism n O  rganizing

PATHOLOGY n L  obar

pneumonia: organism is inhaled or aspirated into peripheral airspaces, where bacteria injure alveolar wall, resulting in local inflammation and progressive consolidation.

Community-Acquired Pneumonia    115

Figure 2.  Bronchopneumonia due to Mycoplasma pneumoniae. Chest radiograph in a 34-year-old woman with cough and malaise shows multiple small patchy opacities in both lower lobes.

Figure 4.  Bronchopneumonia due to Mycoplasma pneumoniae. View of the left lower lobe from a CT scan in a 34-year-old woman with cough and malaise shows small centrilobular nodules, ground-glass opacities, and airspace nodules.

n B  ronchopneumonia:

infectious organisms deposited on epithelium of bronchi produce acute bronchial inflammation with epithelial ulcerations and fibrinopurulent exudate formation; inflammatory reaction rapidly spreads through airways’ walls and into contiguous pulmonary lobules.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  neumonia

is leading cause of death due to infectious disease and sixth most common cause of death in United States.

116    Community-Acquired Pneumonia

n E  stimated

4 million cases of community-acquired pneumonia occur annually in United States. n B  etween 485,000 and 1 million patients each year are hospitalized in the United States for treatment of community-acquired pneumonia. n M  ost common organisms in lobar pneumonia are Streptococcus pneumoniae and Klebsiella pneumoniae. n M  ost common organisms in bronchopneumonia are Staphylococcus aureus, gram-negative organisms, and anaerobes.

Suggested Readings Apisarnthanarak A, Mundy LM: Etiology of community-acquired pneumonia. Clin Chest Med 26:47-55, 2005. Bartlett JG, Dowell SF, Mandell LA, et al: Practice guidelines for the management of community-acquired pneumonia in adults. Infectious Diseases Society of America. Clin Infect Dis 31:347-382, 2000.

COMMUNITY ACQUIRED AND NOSOCOMIAL PNEUMONIA

Herold CJ, Sailer JG: Community-acquired and nosocomial pneumonia. Eur Radiol 14(Suppl 3):E2-E20, 2004. Lutfiyya MN, Henley E, Chang LF, Reyburn SW: Diagnosis and treatment of community-acquired pneumonia. Am Fam Physician 73:442-450, 2006. Sharma S, Maycher B, Eschun G: Radiological imaging in pneumonia: Recent innovations. Curr Opin Pulm Med 13:159-169, 2007. Washington L, Palacio D: Imaging of bacterial pulmonary infection in the immunocompetent patient. Semin Roentgenol 42:122-145, 2007.

Nosocomial Pneumonia DEFINITION: Nosocomial pneumonia is hospital-acquired pneumonia that occurs ≥ 48 hours after

admission.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n V  ast

Findings

n B  ronchopneumonia: patchy areas of consolidation, which

may be lobular, subsegmental, or segmental, although they may coalesce to involve entire lobe or cavitate. n L  ung abscess: single or multiple masses usually measuring 2-6 cm in diameter, often cavitated; internal margins of abscesses smooth (90%) or shaggy (10%); air-fluid levels possible. n N  ecrotizing pneumonia: initially small lucencies within area of consolidated lung, with enlargement of lobe, outward bulging of fissure (“bulging fissure” sign), then lucencies coalescing into large cavity. Utility

n P  osteroanterior

(and lateral when possible) chest radiography should be obtained whenever pneumonia is suspected according to American Thoracic Society guidelines. n R  adiography provides important information regarding extent of pneumonia, presence of complications. n A  lthough certain radiologic patterns are highly suggestive of pneumonia, chest radiography is of limited value in determining specific etiology. n M  anifestations are often delayed, which is particularly important in nosocomial infections (radiographs are often performed within hours of onset of symptoms). n R  adiographic abnormalities may be particularly delayed in immunocompromised patients.

CT

Findings

n B  ronchopneumonia:

centrilobular nodules and branching opacities (“tree-in-bud” pattern) due to bronchiolitis, progressing to airspace nodules, lobular, subsegmental, segmental, or confluent areas of consolidation. n L  ung abscesses: masses with low attenuation in central region or cavitation and rim enhancement after intravenous administration of a contrast agent. Utility n C  an

be helpful in detection, differential diagnosis, and management of patients with pulmonary or pleural complications.

majority of nosocomial pneumonias manifest as bronchopneumonia. n R  adiographic abnormalities are often delayed particularly in immunocompromised patients. n R  adiologic manifestations of nosocomial pneumonia are often indistinguishable from other pulmonary complications commonly seen in these patients. n F  indings

suggestive of pneumonia evident up to 5 days earlier than chest radiographs. n R  ecommended in cases of clinically suspected infection and normal or nonspecific radiographic findings, assessment of suspected complications, and suspicion of underlying lesion.

CLINICAL PRESENTATION n C  haracteristic

clinical findings of pneumonia consist of fever, cough, and purulent sputum. n S  igns and symptoms of pneumonia may be milder or even absent in the elderly.

DIFFERENTIAL DIAGNOSIS n A  cute

respiratory distress syndrome (ARDS) pneumonia n A  cute pulmonary embolism and infarction n A  telectasis n P  ulmonary hemorrhage n O  rganizing

PATHOLOGY n N  osocomial

pneumonia most commonly manifests as bronchopneumonia. n B  ronchopneumonia occurs when infectious organisms are deposited on epithelium of bronchi and produce acute bronchial inflammation with epithelial ulcerations and fibrinopurulent exudate formation.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n M  ain

role of chest radiograph is in confirming presence of parenchymal disease in patients with clinically suspected pneumonia. n M  ain role of CT is in evaluation of immunocompromised patients with suspected pulmonary infection but normal or nonspecific radiographic findings and suspected complications. n R  adiographic appearance of consolidation may be delayed particularly in patients with neutropenia, ­functional defects of granulocytes due to diabetes, alcoholism, or uremia.

117

118    Nosocomial Pneumonia

Figure 1.  Bronchopneumonia. Posteroanterior chest radiograph shows patchy consolidation in the left upper and lower lobes. Note inhomogeneous increased opacity of the left side of the heart compared with the region of the right atrium consistent with consolidation in the retrocardiac region of the left lower lobe. The patient was a 36-year-old woman with bronchopneumonia.

Figure 3.  Bronchopneumonia. High-resolution CT image at the level of the upper zone shows centrilobular nodular and branching opacities (“tree-in-bud” pattern) (arrows), airspace nodules, focal areas of consolidation, and ground-glass opacities. The areas of consolidation have the size and shape consistent with involvement of one or more adjacent lobules (lobular pneumonia). The abnormalities involve the right upper, middle, and lower lobes and, to lesser extent, the left lower lobe. The patient was a 39-year-old man with acute myelogenous leukemia and bacterial bronchopneumonia.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  neumonia

develops in 0.5% to 1.0% of hospitalized patients; mortality in such patients is higher, being estimated at approximately 30%. n P  neumonia is particularly common after surgery and in patients undergoing mechanical ventilation. n C  auses include S. aureus (15% or more), Pseudomonas aeruginosa (20%), Legionella species (1%-40%), K. pneumoniae (15%), and E. coli (5% to 20%).

COMMUNITY ACQUIRED AND NOSOCOMIAL PNEUMONIA

Figure 2.  Lung abscess. Posteroanterior chest radiograph shows large cavity with air-fluid level in the right upper lobe. Also noted are small poorly defined areas of consolidation in the upper lobe. The patient was a 39-year-old man. Blood cultures grew Salmonella.

Figure 4.  Lung abscess. Contrast-enhanced CT demonstrates large area of dense consolidation in the right upper lobe abutting the mediastinum. The consolidation contains a focal area of decreased attenuation with rim enhancement (arrows) characteristic of lung abscess. The patient was a 43-year-old woman with lung abscess secondary to Haemophilus aphrophilus.

Suggested Readings Depuydt P, Myny D, Blot S: Nosocomial pneumonia: Aetiology, diagnosis and treatment. Curr Opin Pulm Med 12:192-197, 2006. Herold CJ, Sailer JG: Community-acquired and nosocomial pneumonia. Eur Radiol 14(Suppl 3):E2-E20, 2004. Hubmayr RD, Burchardi H, Elliot M, et al: Statement of the 4th International Consensus Conference in Critical Care on ICU-Acquired Pneumonia. Chicago, May 2002, Illinois, Intensive Care Med 28:1521-1536, 2002. Ostendorf U, Ewig S, Torres A: Nosocomial pneumonia. Curr Opin Infect Dis 19:327-338, 2006. Porzecanski I, Bowton DL: Diagnosis and treatment of ventilatorassociated pneumonia. Chest 130:597-604, 2006.

Pneumonia in the Immunocompromised Host DEFINITION: Pneumonia that occurs in patient with impaired immune function has higher propensity for diffuse and ­bilateral disease.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  ronchopneumonia:

Findings n F  ocal,

multifocal, or confluent consolidation. pneumonia with cavity formation may occur particularly in infection by gram-negative organisms or Staphylococcus aureus. n P  neumocystis jiroveci (formerly Pneumocystis carinii) pneumonia: bilateral perihilar or diffuse finely granular or ground-glass opacities that may progress to ­consolidation. n C  MV pneumonia: bilateral diffuse areas of ­parenchymal opacification; multiple pulmonary nodules typically

 10

million new cases and >2 million deaths worldwide each year. n M  ajority of cases occur in Southeast Asia and Africa. n R  isk is greatest with altered host cellular immunity (e.g., HIV infection). n A  ctive cases infect 10-15 people annually.

Suggested Readings De Backer AI, Mortelé KJ, De Keulenaer BL, Parizel PM: Tuberculosis: Epidemiology, manifestations, and the value of medical imaging in diagnosis. JBR-BTR 89:243-250, 2006. Lee KS, Song KS, Lim TH, et al: Adult-onset pulmonary tuberculosis: Findings on chest radiographs and CT scans. AJR Am J Roentgenol 160:753-758, 1993.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n T  he

strongest risk factor for tuberculosis is HIV infection. tuberculosis occurs most commonly in children but increasingly is seen in adults. n P  atients may have active tuberculosis and a normal chest radiograph. n P  revalence of normal radiographs in patients with tuberculosis is highest with miliary disease and severe immune compromise. n P  rimary

148

PULMONARY TUBERCULOSIS

Figure 1.  Primary tuberculosis with consolidation and lymph node enlargement in a 24-year-old man. Chest radiograph showing parenchymal consolidation containing air bronchograms (arrows) in the left upper and lower lobes with relative sparing of the lung apex. The left apical soft tissue widening suggests an associated left pleural effusion. Also note the parenchymal opacity and small nodular lesions in right upper lung zone. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 3.  Primary tuberculosis with consolidation and lymph node enlargement in a 24-year-old man. A contrast medium– enhanced CT image at the level of the bronchus intermedius shows parenchymal consolidation containing air bronchograms (arrows) in the left lung. Also note the subcarinal lymph node enlargement (arrowhead), left pleural effusion, and some small nodular opacities in the contralateral right lung. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Leung AN: Pulmonary tuberculosis: The essentials. Radiology 210:307-322, 1999. Leung AN, Müller NL, Pineda PR, FitzGerald JM: Primary tuberculosis in childhood: Radiographic manifestations. Radiology 182: 87-89, 1992.

Primary Tuberculosis    149

Figure 2.  Primary tuberculosis in a 46-year-old woman. Chest radiograph showing a large homogeneous right mediastinal soft tissue opacity. CT showed extensive paratracheal lymphadenopathy.

Figure 4.  Primary tuberculosis in a 46-year-old woman. Contrast medium–enhanced CT image demonstrating extensive paratracheal lymphadenopathy. Note the presence of enlarged lymph nodes with a low-attenuation center and rim enhancement (arrows), a characteristic feature of primary tuberculosis.

Powell DA, Hunt WG: Tuberculosis in children: An update. Adv Pediatr 53:279-322, 2006.

Postprimary Tuberculosis DEFINITION: Pulmonary disease that results from reactivation of a previous focus of tuberculosis

or re-infection.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  atchy

Findings n F  ocal

or patchy heterogeneous consolidation or poorly defined nodules and linear opacities (fibronodular ­pattern). n S  ingle or multiple cavities with air-fluid levels. n M  ainly apical and posterior segments of upper lobes and superior segments of lower lobes. n D  istant nodules representing endobronchial spread. n T  uberculoma: smoothly marginated or spiculated ­nodule. n M  ultiple small nodular densities (1-3 mm) in miliary pattern. n P  leural effusion. n H  ilar or mediastinal lymphadenopathy in 5%-10%. More common in immunocompromised patient. Utility

n U  sed

for initial evaluation and follow-up of patients. be normal or show only mild or nonspecific ­findings.

n M  ay

CT

heterogeneous consolidation in apical and posterior segments of upper lobe. n C  avitation. n T  ree-in-bud pattern on CT. n L  ymphadenopathy in immunocompromised patient.

n M  ore

sensitive in detection and characterization of subtle parenchymal disease and mediastinal lymphadenopathy.

Positron Emission Tomography Findings

n T  uberculoma:

Utility

increased FDG uptake in nodule.

n O  f

limited value in distinguishing active tuberculosis from neoplasm.

CLINICAL PRESENTATION

Findings

n C  entrilobular

nodules and branching linear and nodular opacities (“tree-in-bud” pattern). n P  atchy or lobular areas of consolidation with cavitation. n M  ainly apical and posterior segments of upper lobes and superior segments of lower lobes. n E  ndobronchial spread shown by multilobar centrilobular and “tree-in-bud” opacities. n C  avities usually thick walled; thin walls seen in patients undergoing treatment. n H  ilar or mediastinal lymphadenopathy in 5%-10%; nodes often of low attenuation and may show rim enhancement after intravenous administration of a contrast agent. n T  uberculoma: peripherally enhancing, smoothly marginated or spiculated nodule; may have calcification and cavitation. n M  iliary: multiple randomly distributed nodules (1-3 mm diameter); may have associated septal lines. Utility

n U  sed

in clinically suspected patients with normal or equivocal radiograph.

n M  ay

be asymptomatic or progressive dry cough or productive cough n F  ever, fatigue, weight loss, night sweats n M  ild

DIFFERENTIAL DIAGNOSIS n B  ronchopneumonia n L  obar

pneumonia lymphoma n I nfectious bronchiolitis n W  egener granulomatosis n M  ycobacterium avium-intracellulare complex n P  ulmonary

PATHOLOGY tuberculosis: aerobic, nonmobile, non– spore-forming rod that is highly resistant to drying, acid, and alcohol. n P  rogressive extension and enlargement of foci of inflammation and necrosis. n M  ycobacterium

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n T  he

strongest risk factor for tuberculosis is HIV infection. may have active tuberculosis and a normal chest radiograph. n N  ormal radiographs occur most often with miliary disease and in severely immunocompromised patients. n P  atients

150

PULMONARY TUBERCULOSIS

Figure 1.  Postprimary tuberculosis. Chest radiograph shows a focal parenchymal opacity and small nodular clustering in the right upper lobe. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 3.  Cavitary postprimary tuberculosis in a 30-year-old man. CT scan at the level of the great vessels shows cavitating (arrows) and noncavitating consolidation, “tree-in-bud” opacities (arrowheads) and variably sized nodular lesions (curved arrows) in the right upper lobe. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Postprimary Tuberculosis    151

Figure 2.  Postprimary tuberculosis. Chest radiograph shows extensive areas of small nodular clustering in both lungs. Also note the segmental consolidation in the right upper lobe and a left pleural effusion. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 4.  Miliary tuberculosis in a 27-year-old woman. A CT scan at the level of the main bronchi demonstrates the random distribution of numerous small nodules. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea).

152    Postprimary Tuberculosis

n E  rosion

of cavity into bronchus with resultant endobronchial spread. n N  ecrotizing granulomas.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n >  10

million new tuberculosis cases, with >2 million deaths worldwide every year. n M  ajority of cases occur in Southeast Asia and Africa. n R  isk of active tuberculosis is greatest with altered host cellular immunity (e.g., HIV infection). n R  eactivation of latent infection occurs in 5% of infected population.

PULMONARY TUBERCULOSIS

Suggested Readings Kim HY, Song KS, Goo JM, et al: Thoracic sequelae and complications of tuberculosis. RadioGraphics 21:839-858, 2001;discussion 859-860. Krysl J, Korzeniewska-Koesela M, Müller NL, FitzGerald JM: Radiologic features of pulmonary tuberculosis: An assessment of 188 cases. Can Assoc Radiol J 45:101-107, 1994. Kwong JS, Carignan S, Kang EY, et al: Miliary tuberculosis: Diagnostic accuracy of chest radiography. Chest 110:339-342, 1996. Lee JY, Lee KS, Jung KJ, et al: Pulmonary tuberculosis: CT and pathologic correlation. J Comput Assist Tomogr 24:691-698, 2000. Leung AN: Pulmonary tuberculosis: The essentials. Radiology 210:307-322, 1999. Maartens G, Wilkinson RJ: Tuberculosis. Lancet 370:2030-2043, 2007. Murayama S, Murakami J, Hashimoto S, et al: Noncalcified pulmonary tuberculomas: CT enhancement patterns with histological correlation. J Thorac Imaging 10:91-95, 1995.

Sequelae and Long-Term Complications of Tuberculosis DEFINITION: Complications and sequelae that result from pulmonary tuberculosis. IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  ronchiectasis

Findings

n P  arenchymal

nodules or consolidation. and calcifications, atelectasis, scarring, architectural distortion. n P  leural effusion, thickening (fibrothorax), ­calcification. n A  cute respiratory distress syndrome: extensive ­bilateral ground-glass opacities or consolidation with miliary or endobronchial pattern. n C  ysts: airspaces with well-defined walls; may be in background of consolidation. n C  onstrictive pericarditis: enlargement of cardiopericardial silhouette, extensive pericardial calcification, pleural effusions. n T  uberculous spondylitis: paraspinal soft tissue ­densities. n F  ibrosis

Utility

n U  sed

for initial evaluation and follow-up of patients. n M  ay be normal or show only mild or nonspecific ­findings.

and bronchial stenosis consolidation n C  hronic pleural effusion n C  avitation and intracavitary mass n P  ulmonary artery aneurysm n P  rogressive

n M  ore

sensitive in detection and characterization of subtle parenchymal disease and mediastinal lymphadenopathy. n S  uperior to radiography in demonstrating pulmonary, pleural, cardiac, and chest wall complications.

Angiography Findings

n R  asmussen

artery

Utility

n U  sually

aneurysm: focal dilatation of pulmonary

only performed before coil embolization

CT

MRI

n P  arenchymal

n T  uberculous

Findings

consolidation with multiple cysts. n R  eticulonodular pattern (fibronodular tuberculosis). n A  rchitectural distortion, fibrosis, and scarring; mildly enlarged and calcified lymph nodes. n B  ronchiectasis: unilateral or bilaterally asymmetric, usually most severe in upper lobe. n T  racheobronchial stenosis: thickening of bronchial wall and luminal narrowing. n R  asmussen aneurysm: focal dilatation of pulmonary artery often associated with cavity. n C  onstrictive pericarditis: pericardial effusion and thickening; extensive pericardial calcification; distortion of right ventricle; pleural effusions. n E  mpyema necessitatis: fluid collections in pleura and chest wall. n T  uberculous spondylitis: paraspinal soft tissue mass with bony destruction. Utility

n U  sed

in clinically suspected patients with normal or equivocal radiograph.

Findings

spondylitis: paraspinal soft tissue mass may show intraspinal extension n S  uperior to CT in demonstrating extent of tuberculous spondylitis and extension into spinal canal

CLINICAL PRESENTATION n M  ay

be asymptomatic or progressive dry cough or productive cough n F  ever, fatigue, weight loss, night sweats n H  emoptysis due to bronchiectasis, aspergilloma, or Rasmussen aneurysm n M  ild

DIFFERENTIAL DIAGNOSIS n B  ronchopneumonia n L  obar

pneumonia cancer n W  egener granulomatosis n M  ycobacterium avium-intracellulare complex n L  ung

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n T  he

strongest risk factor for tuberculosis is HIV infection. may have active tuberculosis and normal chest radiograph. n T  he most common sequelae of previous tuberculosis are areas of scarring, bronchiectasis, calcified ­parenchymal focus, and calcified ipsilateral lymph nodes. n P  atients

153

154    Sequelae and Long-Term Complications of Tuberculosis

Figure 1.  Tracheobronchial tuberculosis in a 31-year-old woman. Minimum intensity projection image shows luminal narrowing of the lower portion of the trachea (arrows) and an obliterated lumen of the right main bronchus (arrowhead). (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 3.  Tuberculous empyema necessitatis in a 29-year-old woman. CT scan image demonstrates a fluid collection in the extrapleural subcostal tissue (arrows) and in the right chest wall (arrowheads). (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

PULMONARY TUBERCULOSIS

Figure 2.  Rasmussen aneurysm in a 60-year-old man with chronic destructive pulmonary tuberculosis. A contrastenhanced CT scan at the level of the bronchus intermedius shows a contrast-filling aneurysm (arrow) within parenchymal consolidation in a superior segment of the left lower lobe. Also note the enlarged subcarinal lymph nodes (arrowheads). (Courtesy of Dr. Yeon Joo Jeong, Pusan National University Hospital, Pusan, Korea.)

Figure 4.  Tuberculous spondylitis in a 79-year-old man. A contrast-enhanced CT scan at the level of the caudate lobe of the liver shows a calcified, heterogeneous, and low-attenuation soft tissue opacity in the paraspinal region bilaterally, along with associated destruction of the vertebral body. Also note the intraspinal extension (arrow) of the soft tissue abnormality with associated cord (arrowhead) compression. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

PULMONARY TUBERCULOSIS

Sequelae and Long-Term Complications of Tuberculosis    155

PATHOLOGY tuberculosis is an aerobic, nonmobile, non–spore-forming rod that is highly resistant to drying, acid, and alcohol. n A  ctive M. tuberculosis infection has lymphatic and hematogenous spread. n P  rogressive extension of foci of inflammation and necrosis occurs. n H  ealing may result in fibrosis, scar formation, calcification, and architectural distortion. n O  ther complications include bronchiectasis, bronchial stenosis, aspergilloma, Rasmussen aneurysm, fibro­ thorax, empyema, empyema necessitatis, and constrictive pericarditis. n M  ycobacterium

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n >  10

million new tuberculosis cases and >2 million deaths worldwide each year. n M  ajority of tuberculosis occurs in Southeast Asia and Africa.

n M  ost

common sequelae of previous tuberculosis are areas of scarring, bronchiectasis, calcified parenchymal focus, and calcified ipsilateral lymph nodes. n C  hronic cavitation and bronchiectasis due to previous tuberculosis are the most common underlying causes of aspergilloma.

Suggested Readings Choi JA, Hong KT, Oh YW, et al: CT manifestations of late sequelae in patients with tuberculous pleuritis. AJR Am J Roentgenol 176:441-445, 2001. Im JG, Itoh H, Shim YS, et al: Pulmonary tuberculosis: CT findings— early active disease and sequential change with antituberculous therapy. Radiology 186:653-660, 1993. Kim HY, Song KS, Goo JM, et al: Thoracic sequelae and complications of tuberculosis. RadioGraphics 21:839-858, 2001; discussion 859-860. Kim Y, Lee KS, Yoon JH, et al: Tuberculosis of the trachea and main bronchi: CT findings in 17 patients. AJR Am J Roentgenol 168:1051-1056, 1997. Poey C, Verhaegen F, Giron J, et al: High resolution chest CT in tuberculosis: Evolutive patterns and signs of activity. J Comput Assist Tomogr 21:601-607, 1997.

PART 11 

 ONTUBERCULOUS (ATYPICAL) N MYCOBACTERIAL INFECTION

Mycobacterium avium-intracellulare Complex DEFINITION: Pulmonary disease that occurs secondary to infection with Mycobacterium avium-intracellulare complex. IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  ronchiectasis

Findings

n C  avitary

form: focal consolidation with thin-walled cavities; may be superimposed on chronic lung disease. n M  ild form (Lady Windermere syndrome): small nodules or foci of consolidation with bronchiectatic changes. n H  ot tub lung: patchy ground-glass opacities and small poorly defined nodules. Utility

n I nitial

modality and used for follow-up spectrum and severity of findings n M  ay be normal and usually nonspecific n R  adiographic progression of months or years n R  adiographic manifestations of cavitary form indistinguishable from those of tuberculosis n W  ide

CT

and nodules in the middle lobe and/or lingula. n S  lowly progressive bronchiectasis and tree-in-bud pattern. n F  ocal consolidation and cavitation superimposed on top of chronic lung disease. n H  ot tub lung: ground-glass opacities with centri­ lobular nodules and air trapping. n H  igh-resolution

CT findings of hot tub lung similar to those of hypersensitivity pneumonitis.

CLINICAL PRESENTATION n M  ay

be asymptomatic of pulmonary infection n U  nexplained exacerbation of symptoms in patient with chronic disease n H  ot tub lung: subacute dry cough and dyspnea in hot tub user n S  ymptoms

Findings

n C  avitary

form: cavitary lesions or cavitation in small nodules. n O  ften underlying chronic lung disease. n B  ronchiectatic form: Mild multilobar cylindrical bronchiectasis with right middle lobe and lingular predominance. n S  mall nodules in random, centrilobular or “tree-inbud” pattern; or small foci of consolidation. n A  reas of decreased attenuation pattern reflecting obliterative small airways disease possible. n H  ot tub lung: ill-defined, low attenuation, centrilobular nodules, patchy ground-glass opacities, and air trapping. n U  ncommon features: fibrosis, pleural thickening or effusion, mediastinal lymphadenopathy. Utility

n M  ore

sensitive than radiography. nonspecific, but combination of findings highly suggestive in patients with Lady Windermere syndrome. n H  igh-resolution CT manifestations of cavitary form indistinguishable from those of tuberculosis. n F  indings

DIFFERENTIAL DIAGNOSIS n P  ostprimary

tuberculosis

n B  ronchopneumonia n H  ypersensitivity

pneumonitis

PATHOLOGY n S  pectrum

of pulmonary infection secondary to Mycobacterium avium-intracellulare complex. n C  avitary form: upper lobe cavitary lesions, granulomatous inflammation with caseation necrosis. n B  ronchiectatic form: granulomatous inflammation, bronchiectasis. n H  ot tub lung: infection by aerosolized droplets with resultant granulomatous hypersensitivity reaction.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n D  ecision

to treat infection is complex and influenced by patient-based factors. to drug treatment is highly variable. n C  T is particularly helpful in demonstrating slowly progressive parenchymal disease and ­ bronchiectasis in patients with bronchiectatic form of infection. n S  ensitivity

156

NONTUBERCULOUS (ATYPICAL)

Mycobacterium avium-intracellulare Complex    157

Figure 2.  M. avium-intracellulare complex infection. CT through the lung apices shows mild cylindrical bronchiectasis, a few bilateral centrilobular nodules, a small cavitating lesion in the periphery of the right apex, and small foci of consolidation. Note the loss of volume in the left upper lobe. (Courtesy of Dr. David M. Hansell, London, UK) Figure 1.  M. avium-intracellulare complex. Chest radiograph demonstrates widespread consolidation and a cavitating lesion in the right mid lung zone in a patient with M. avium-intracellulare complicating severe chronic obstructive pulmonary disease. (Courtesy of Dr. David M. Hansell, London, UK)

Figure 3.  M. avium-intracellulare complex infection with a “Lady Windermere” distribution. CT image at the level of right inferior pulmonary vein shows bilateral bronchiectasis. Groundglass opac­ities and mild consolidation are present in the right middle lobe, lin­gula, and left lower lobe. Also evident are small nodular opacities and a few “tree-in-bud” opacities. The patient was a 67-year-old woman.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n I ncidence

of nontuberculous mycobacterial infection: 0.5-10 per 100,000 population. n C  avitary form: tendency to affect males with smokingrelated chronic lung disease. n B  ronchiectatic form: affects females > age 50 years with no preexisting disease or patients with underlying bronchiectasis. n H  ot tub lung: affects otherwise fit and relatively healthy hot tub users.

Suggested Readings Diagnosis and treatment of disease caused by nontuberculous mycobacteria. This official statement of the American Thoracic Society was approved by the Board of Directors, March 1997. Medical

Figure 4.  Hot tub lung. CT through the lower lobes of a patient with biopsy-proven hot tub lung shows diffuse ground-glass opacity and indistinct small nodules measuring 1-2 mm in diameter and resembling subacute hypersensitivity pneumonitis.

Section of the American Lung Association. Am J Respir Crit Care Med 156:21-25, 1997. Hartman TE, Jensen E, Tazelaar HD, et al: CT findings of granulomatous pneumonitis secondary to Mycobacterium avium-intracellulare inhalation: “Hot tub lung.” AJR Am J Roentgenol 188:10501053, 2007. Hartman TE, Swensen SJ, Williams DE: Mycobacterium avium-intracellulare complex: Evaluation with CT. Radiology 187:23-26, 1993. Hollings NP, Wells AU, Wilson R, Hansell DM: Comparative appearances of non-tuberculous mycobacteria species: A CT study. Eur Radiol 12:2211-2217, 2002. Jeong YJ, Lee KS, Koh WJ, et al: Nontuberculous mycobacterial pulmonary infection in immunocompetent patients: Comparison of thin-section CT and histopathologic findings. Radiology 231:880886, 2004. Waller EA, Roy A, Brumble L, et al: The expanding spectrum of Mycobacterium avium complex–associated pulmonary disease. Chest 130:1234-1241, 2006.

Unusual Nontuberculous Mycobacteria DEFINITION: Pulmonary disease that occurs secondary to infection with various nontuberculous Mycobacterium species. IMAGING

DIAGNOSTIC PEARLS

Radiography

n C  onsolidation

Findings

n C  onsolidation n C  avities n S  mall

Utility

with cavitation nodules with variable pattern n B  ackground of chronic parenchymal disease n S  mall

with or without air-fluid levels nodules

n I nitial

modality and used for follow-up spectrum and severity of findings: can be normal n F  indings resemble those of reactivation tuberculosis n W  ide

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

CT

n I ncidence

Findings

n C  onsolidation

n B  ronchiectasis

with cavities

n C  entrilobular n May

Utility n C  T

nodules and “tree-in-bud” pattern have background of chronic lung disease

is more sensitive than radiography. resemble those of tuberculosis.

n F  indings

CLINICAL PRESENTATION n M  ay

be asymptomatic n S  ymptoms of pulmonary infection n R  apid decline in patients with existing disease (e.g., cystic fibrosis)

DIFFERENTIAL DIAGNOSIS n P  ostprimary

tuberculosis avium-intracellulare complex

n M  ycobacterium

PATHOLOGY

of nontuberculous mycobacterial infection is 0.5-10 per 100,000 population. n P  revalence differs globally (e.g., M. malmoense is common in Europe; M. kansasii occurs in southern United States). n M  . kansasii is second most common pathogen in nontuberculous mycobacterial infection. n M  . kansasii infection is seen in HIV-positive individuals and middle-aged men.

Suggested Readings Diagnosis and treatment of disease caused by nontuberculous mycobacteria. This official statement of the American Thoracic Society was approved by the Board of Directors, March 1997. Medical Section of the American Lung Association. Am J Respir Crit Care Med 156:21-25, 1997. Ellis SM, Hansell DM: Imaging of non-tuberculous (atypical) mycobacterial pulmonary infection. Clin Radiol 57:661-669, 2002. Erasmus JJ, McAdams HP, Farrell MA, Patz EF: Pulmonary nontuberculous mycobacterial infection: Radiologic manifestations. RadioGraphics 19:1487-1503, 1999. Hollings NP, Wells AU, Wilson R, Hansell DM: Comparative appearances of non-tuberculous mycobacteria species: A CT study. Eur Radiol 12:2211-2217, 2002.

n P  ulmonary

infection secondary to various ubiquitous environmental opportunistic nontuberculous Mycobacterium species. n S  everity of disease largely determined by immune ­status or supervening infection.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n D  ecision

to treat infection is complex and influenced by patient-based factors. to drug treatment is highly variable.

n S  ensitivity

158

NONTUBERCULOUS (ATYPICAL)

Figure 1.  M. kansasii infection. CT image through the upper lobes of a patient with background centrilobular emphysema and M. kansasii infection demonstrates thick-walled cavities at the right lung apex and bilateral centrilobular nodular opacities. The appearance is similar to that of reactivation tuberculosis. (Courtesy of Dr. David M. Hansell, London, UK)

Figure 3.  Cystic fibrosis and M. chelonae infection. CT image at the level of inferior pulmonary veins of a patient with M. chelonae infection shows extensive bronchiectasis and right lower lobe nodule. (Courtesy of Dr. David M. Hansell, London, UK)

Unusual Nontuberculous Mycobacteria    159

Figure 2.  M. xenopi infection. CT image through the lung apices shows cavitating lesions on a background of severe centrilobular emphysema. (Courtesy of Dr. David M. Hansell, London, UK)

Figure 4.  M. szulgai infection in an HIV-infected patient. CT image shows multiple cavitating lesions in a HIV-infected patient. (Courtesy of Dr. David M. Hansell, London, UK)

Part 12 

FUNGAL INFECTIONS

Aspergillosis DEFINITION: Aspergillosis is a lung infection caused by Aspergillus fungi. IMAGING

DIAGNOSTIC PEARLS

Radiography

n A  spergilloma:

Findings

n A  spergilloma:

upper lobe rounded or oval, mobile mass within cavity with surrounding crescent of air (air crescent sign). n A  llergic bronchopulmonary aspergillosis: bronchiectasis seen as “finger-in-glove” or tube-like opacities corresponding to mucus plugs in dilated central bronchi. n S  egmental or lobar consolidation in chronic necrotizing aspergillosis. n P  oorly defined bilateral nodular opacities evident in airway-invasive aspergillosis. n A  ngioinvasive aspergillosis: multiple, ill-defined nodular opacities; air crescent sign. Utility

n H  elpful

ment.

in detecting disease and monitoring of treat-

CT

Findings n U  pper

lobe mass within a cavity in aspergilloma. with mucus plugs resulting in branching opacities that may have increased attenuation. n S  egmental or lobar consolidation in chronic necrotizing aspergillosis. n “  Tree-in-bud” appearance in airway-invasive aspergillosis. n A  ngioinvasive aspergillosis: nodules without and with halo of ground-glass attenuation (CT halo sign). n B  ronchiectasis

Utility

n D  etects aspergilloma too small to be seen on radiography. n M  ore

sensitive and specific than radiography in the diagnosis of invasive aspergillosis.

CLINICAL PRESENTATION n H  emoptysis

(aspergilloma, chronic necrotizing aspergillosis) n W  heezing, expectoration of mucus plugs (allergic bronchopulmonary aspergillosis)

upper lobe, rounded or oval, mobile mass within cavity with surrounding crescent of air (air crescent sign). n A  llergic bronchopulmonary aspergillosis: central and predominantly upper lobe bronchiectasis seen as “finger-in-glove” or tube-like opacities corresponding to mucus plugs in dilated central bronchi. n A  irway-invasive aspergillosis: tree-in-bud pattern and patchy consolidation. n A  ngioinvasive aspergillosis: nodules with halo of ground-glass attenuation (CT halo sign).

n C  hronic

productive cough, fatigue, dyspnea (chronic necrotizing aspergillosis) n B  ronchiolitis and bronchopneumonia (airway-invasive aspergillosis) n F  ever (angioinvasive aspergillosis)

DIFFERENTIAL DIAGNOSIS n B  ronchopneumonia n B  ronchiectasis n S  eptic

embolism

PATHOLOGY n A  spergilloma

is composed of fungal mycelia, inflammatory cells, fibrin, mucus, and tissue debris and develops in preexisting lung cavity. n A  irway colonization causes persistent inflammation and fibrosis leading to bronchiectasis, mucoid impaction, and parenchymal scarring in allergic bronchopulmonary aspergillosis. n A  irway-invasive aspergillosis is characterized by presence of fungi deep to airway basement membrane. n A  ngioinvasive aspergillosis is caused by hyphal invasion of blood vessels resulting in infarction and ­necrosis.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW n A  llergic

bronchopulmonary aspergillosis occurs mainly in patients with asthma or cystic fibrosis and results from hypersensitivity reaction to Aspergillus antigens. n N  odules with a halo of ground-glass attenuation on CT in severely neutropenic patients are highly suggestive of angioinvasive aspergillosis. n C  T is superior to chest radiography in the diagnosis of Aspergillus-related airway or parenchymal disease.

160

Aspergillosis    161

F UNGAL INFECTIONS

Figure 1.  Aspergilloma. A 59-year-old woman with previous right mastectomy and right upper lobectomy presented with cough and weight loss. High-resolution CT scan shows a large mycetoma within the cavity. Aspergillus fumigatus was recovered at bronchoscopy.

Figure 3.  Aspergillus bronchiolitis and bronchopneumonia. High-resolution CT scan shows localized area of ground-glass attenuation in the right lung and bilateral, poorly defined small nodular opacities, and branching opacities (“tree-in-bud”) (arrows). Open-lung biopsy showed Aspergillus bronchiolitis and bronchopneumonia. The patient was a 52-year old man who had undergone bone marrow transplantation. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 2.  Allergic bronchopulmonary aspergillosis. A 31-year-old man presented with a history of asthma, recurrent pneumonias, and expectoration of brownish mucus plugs. CT image shows bilateral central bronchiectasis and a left upper lobe mucus plug (arrow). (Courtesy of Dr. Thomas E. Hartman, Mayo Clinic, Rochester, MN)

Figure 4.  CT halo sign in invasive pulmonary aspergillosis. Magnified view of the left lung from a high-resolution CT shows nodule with surrounding ground-glass attenuation (CT halo sign) (arrows). The patient was a 33-year-old man with acute leukemia, severe neutropenia, and angioinvasive pulmonary aspergillosis.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

n A  ngioinvasive

is most common cause of fungus ball. bronchopulmonary aspergillosis occurs in 7%-14% of corticosteroid-dependent asthmatics and 6% of patients with cystic fibrosis. n S  emi-invasive or chronic necrotizing aspergillosis primarily occurs in patients with underlying chronic lung disease, with chronic debilitating illness, or on prolonged corticosteroid therapy. n A  irway-invasive aspergillosis occurs most commonly in neutropenic patients.

Suggested Readings

n A  spergillus n A  llergic

aspergillosis primarily affects severely immunocompromised patients with neutropenia.

Chong S, Lee KS, Yi CA, et al: Pulmonary fungal infection: Imaging findings in immunocompetent and immunocompromised patients. Eur J Radiol 59:371-383, 2006. Franquet T, Muller NL, Gimenez A, et al: Spectrum of pulmonary aspergillosis: Histologic, clinical, and radiologic findings. RadioGraphics 21:825-837, 2001. Waite S, Jeudy J, White CS: Acute lung infections in normal and immunocompromised hosts. Radiol Clin North Am 44:295-315, 2006. Wheat LJ, Goldman M, Sarosi G: State-of-the-art review of pulmonary fungal infections. Semin Respir Infect 17:158-181, 2002.

Blastomycosis DEFINITION: Blastomycosis is infection caused Blastomyces dermatitidis. IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  ulmonary

Findings

n V  aried and nonspecific findings: consolidation, masses,

nodules, cavitation, and interstitial changes. common appearance: patchy or confluent segmental or subsegmental airspace consolidation, which often has ill-defined margins; air bronchograms.

n M  ost

masses containing air bronchograms. or confluent airspace consolidation with ill-defined margins, air bronchograms, and usually segmental or subsegmental. n E  ndemic regions: southeastern and south central United States, Central Canada, South America. n P  atchy

Utility

n F  indings

often resemble those of community-acquired pneumonia but granulomatous infection should be suspected if findings progress or are slow to resolve. n M  asses may be confused with bronchogenic carcinoma. n C  hest radiography helps detect disease.

n V  errucous

skin lesion with raised, irregular border drainage or ulcerative lesion with sharp, heaped-up border and exudate at its base.

DIFFERENTIAL DIAGNOSIS

CT

n C  ommunity-acquired

n P  ulmonary

n P  ulmonary

Findings

masses that frequently contain air bronchograms. n N  odules 2 cm diameter), irregular or lobulated margins, contiguous tracheal wall thickening, and mediastinal invasion. n P  olypoid

imaging test for patients presenting with central airway symptoms n O  n radiography, careful scrutiny of airway needed because lesions often overlooked n D  ifficult to distinguish intrinsic tracheal abnormality from extrinsic compression

MRI

CT

n I ntermediate

Findings

n P  olypoid

or sessile intraluminal mass of soft tissue density n N  ecrosis and ulceration n H  amartoma or lipoma: fat within a lesion n C  hondroid tumor: calcification within a lesion n R  egional lymph node metastases and complications (tracheoesophageal fistula) n C  ircumferential tracheal wall thickening and luminal narrowing Utility

n M  ultidetector

CT is imaging modality of choice for detection and staging of tracheal neoplasms. n C  T has high sensitivity (>97%) for detecting tracheal neoplasms. n C  T has limited specificity in distinguishing between neoplastic cell types. n A  ssessment of submucosal spread and local extratracheal invasion is possible. n M  ultiplanar and 3D reconstructions complement axial images by improving assessment of craniocaudal extent of disease and degree of extratracheal involvement. n C  T does not reliably detect microscopic mediastinal invasion or neural invasion.

Findings

signal intensity on T1-weighted images signal intensity on T2-weighted images n T  racheal wall thickening and luminal narrowing n H  igh

Utility

n S  econd-line,

problem-solving tool for assisting in tissue characterization and assessment of mediastinal invasion.

CLINICAL PRESENTATION n T  umor

is clinically silent until tracheal lumen is narrowed by approximately 75%. n S  ymptoms include dyspnea, cough, hemoptysis, wheezing, and stridor. n S  quamous cell carcinoma: average age at presentation is between 50 and 60 years. n A  denoid cystic carcinoma: average age at presentation is between 40 and 50 years.

DIFFERENTIAL DIAGNOSIS n W  egener n T  racheal

granulomatosis stenosis

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Tracheal



n Clinical



neoplasm should be considered in patients with a history of “adult-onset asthma.” symptoms of central airway obstruction overlap with other tracheal disorders, including tracheal stenosis and tracheomalacia. n Biopsy is usually necessary to establish the diagnosis. n Surgery is the treatment of choice. n Majority of tracheal neoplasms are malignant in adults. n CT is the imaging modality of choice for detection and staging.

433

434    Tracheal Neoplasms

Figure 1.  Tracheal neoplasm. Lateral chest radiograph demonstrates a smoothly marginated, round mass within the tracheal lumen. (Courtesy of Dr. Phillip M. Boiselle, Harvard Medical School, Boston)

Figure 3.  Malignant tracheal neoplasm. CT image at carina demonstrates a lobulated intraluminal mass with direct invasion through airway wall (anterior). Also note enlarged precarinal lymph node (N), left lower lobe consolidation, and bilateral pleural effusions. Final diagnosis was adenoid cystic carcinoma. (Courtesy of Dr. Phillip M. Boiselle, Harvard Medical School, Boston)

TRACHEAL ABNORMALITIES

Figure 2.  Tracheal hamartoma. CT image demonstrates a fatattenuation tracheal mass (arrow) arising from the left lateral wall. Final diagnosis was lipomatous hamartoma. (Courtesy of Dr. Phillip M. Boiselle, Harvard Medical School, Boston)

Figure 4.  Coronal reformatted image demonstrates a mass (M) arising at level of carina (asterisk), with extension into right main bronchus (arrow) and paratracheal soft tissues. This image provided a better assessment of extent of disease than axial images and aided preoperative planning. Final diagnosis was adenoid cystic carcinoma. (Courtesy of Dr. Phillip M. Boiselle, Harvard Medical School, Boston)

Tracheal Neoplasms    435

TRACHEAL ABNORMALITIES

n T  racheobronchial n T  uberculosis

amyloidosis

n M  etastases

PATHOLOGY n A  pproximately

80% of tracheal neoplasms are malignant and the great majority are adenoid cystic carcinomas and squamous cell carcinomas. n B  enign neoplasms include papillomas, hamartomas, schwannomas, hemangiomas, and chondromas.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  rimary

tracheal neoplasms are rare.

n P  rimary

tracheal tumor is roughly 180 times less common than a primary lung cancer. n S  quamous cell carcinoma and squamous cell papilloma have a male predominance and are associated with cigarette smoking. n A  denoid cystic carcinoma has no sex predilection and is not related to smoking.

Suggested Readings Kwak SH, Lee KS, Chung MJ, et al: Adenoid cystic carcinoma of the airways: Helical CT and histopathologic correlation. AJR Am J Roentgnol 183:277-281, 2004. McCarthy MJ, Rosado-de-Christenson ML: Tumors of the trachea. J Thorac Imaging 10:180-198, 1995. Parsons RB, Milestone BN, Adler LP: Radiographic assessment of airway tumors. Chest Surg Clin North Am 13:63-77, 2003.

Tracheomalacia DEFINITION: Tracheomalacia is characterized by increased compliance and excessive collapsibility of the trachea due to weakness of the airway walls and/or supporting cartilage. IMAGING

DIAGNOSTIC PEARLS

Radiography

n G  reater

Findings

n I nspiratory

Utility

n M  ay

radiograph is usually normal

be detected on radiograph

CT

than 50% reduction in the cross-sectional lumen of the trachea during expiration n Complete expiratory collapse n C  rescentic, “frown-like” configuration of tracheal lumen with 50% reduction in cross-sectional lumen of trachea during expiration. n C  rescentic, “frown-like” configuration of tracheal lumen with 1 cm (large opacities) n A  typical: lower lung reticulation, decreased lung volumes, traction bronchiectasis, and honeycombing n H  ilar and mediastinal lymphadenopathy n C  alcification of nodules possible n C  omplicated

Utility

n C  hest

radiograph usually only imaging modality required in diagnosis and follow-up n R  elatively insensitive to early disease n D  escribes findings using International Labour Organization (ILO) 2000 terminology n D  isease radiographically indistinguishable from silicosis, although nodules may be less well defined and granular

CT

Findings n S  imple

type: small nodules with upper lobe predominance that may occasionally calcify n S  mall branching linear or ill-defined punctate attenuation n S  ubpleural nodules adjacent to visceral pleura (pseudoplaques) n C  omplicated type: lesions >1 cm (large opacities) n M  ediastinal or hilar lymphadenopathy Utility n C  T,

particularly volumetric CT, superior to chest radiography in demonstrating presence of nodules n S  imilar findings to silicosis

CLINICAL PRESENTATION n U  sually

asymptomatic n C  hronic cough that persists even after patient leaves the workplace n C  oal dust exposure >20 years

nodular opacities mainly in upper lobes nodules adjacent to visceral pleura (pseudoplaques) n C  oal miner n S  ubpleural

DIFFERENTIAL DIAGNOSIS n S  ilicosis

n S  arcoidosis

n T  uberculosis n W  elder’s

pneumoconiosis (welder’s lung)

PATHOLOGY n H  istologic

landmark: black coal dust macule represents focal deposition of coal dust and pigment-laden macrophages around respiratory bronchioles. n M  acules enlarge and coalesce, forming a discrete network of interstitial fibrosis, resulting in respiratory bronchiole dilatation and emphysema. n I ncreased exposure to coal mine dust causes development of nodular lesions at bifurcations of respiratory bronchiole against background of macules. n N  odules are composed of heavily coal dust–laden macrophages interlaced with collagen fibers oriented in a haphazard manner microscopically. n W  ith chronic dust exposure, simple nodules coalesce to produce black, rubbery parenchymal fibrous masses resulting in complicated disease and progressive massive fibrosis.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  revalence n P  redicted

of 2%-12% in American coal miners prevalence of 9% in British coal miners

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

486

n ILO

2000 International Classification of Radiographs of Pneumoconiosis is the most widely accepted ­ lassification of extent of disease. c n Chest radiograph is the first and foremost imaging modality in initial evaluation and follow-up of suspected or proven cases. n CT is helpful in case assessment and suspected pulmonary complications (carcinoma, pulmonary ­hypertension, right-sided heart failure, tuberculosis). n PET/CT may be helpful in evaluating complicated disease but may be falsely positive in progressive massive fibrosis. n Lung function impairment is related to the degree of nodulation, progressive massive fibrosis, and ­emphysema.

SILICOSIS AND COAL WORKER’S PNEUMOCONIOSIS

Figure 1.  Coal worker’s pneumoconiosis. Ten-millimeter collimation CT scan shows small nodules in both lungs. Subpleural nodules mimicking pleural plaques are evident posteriorly. (Courtesy of Dr. Martine Remy-Jardin, Centre Hospitalier Regional et Universitaire de Lille, Lille, France; from Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

n A  typical

type seen in 10%-20%, with higher risk of carcinoma n I ncreased risk of developing active tuberculosis and nontuberculous mycobacterial infections

Suggested Readings Chong S, Lee KS, Chung MJ, et al: Pneumoconiosis: Comparison of imaging and pathologic findings. RadioGraphics 26:59-77, 2006. Gevenois PA, Pichot E, Dargent F, et al: Low grade coal worker’s pneumoconiosis: Comparison of CT and chest radiography. Acta Radiol 35:351-356, 1994.

Coal Worker’s Pneumoconiosis    487

Figure 2.  Coal worker’s pneumoconiosis. On high-resolution CT the nodules are more difficult to distinguish from vessels. The nodular and branching opacities have a centrilobular distribution (arrows). The subpleural pseudoplaques are defined better with high-resolution CT. (Courtesy of Dr. Martine Remy-Jardin, Centre Hospitalier Regional et Universitaire de Lille, Lille, France; from Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

International Labour Office Guidelines for the use of ILO International Classification of Radiographs of Pneumoconiosis: Occupational Safety and Health Series No 22. Geneva, 2000, International Labor Office. Remy-Jardin M, Remy J, Farre I, Marquette CH: Computed tomographic evaluation of silicosis and coal workers’ pneumoconiosis. Radiol Clin North Am 30:1155-1176, 1992. Vallyathan V, Brower PS, Green FHY, Attfield MD: Radiographic and pathologic correlation of coal workers’ pneumoconiosis. Am J Respir Crit Care Meal 154:741-748, 1996.

Part 49 

ASBESTOS-RELATED DISEASE

Asbestos-Related Pleural Plaques DEFINITION: Pleural plaques are dense, almost acellular collagen with a basketweave pattern; they are usually bilateral and may be asymmetric. IMAGING

DIAGNOSTIC PEARLS

Radiography

n F  ocal,

Findings n F  ocal,

pleural-based opacities with irregular margins plaques or of fine or coarse nodularity that can be round, elliptical, or irregularly shaped n C  alcification: punctate, linear, or coalescent n S  mooth-surfaced

Utility

n O  nly

allows detection of plaques in 50%-80% of cases

n L  imited specificity in cases of mild pleural disease, which

may be difficult to distinguish from extrapleural fat

CT

pleural-based opacities with irregular margins distribution: posterolateral chest wall, lateral chest wall, dome of diaphragm, and paravertebral pleura n U  sually bilateral; may be asymmetric n L  atency time for development of pleural plaques is 20-30 years n C  alcification is seldom evident until >30 years after exposure. n T  ypical

PATHOLOGY

Findings

n C  ircumscribed

areas of pleural thickening separated from underlying ribs and extrapleural soft tissues by thin layer of fat n C  alcification Utility

n H  igh-resolution

CT has greater sensitivity than conventional CT or chest radiography for detection of pleural plaques. n D  iaphragmatic pleural plaques are more readily detected on coronal or sagittal reformatted images of volumetric high-resolution performed on multidetector scanner.

n P  leural

plaques are dense, almost acellular collagen with basketweave pattern; they are usually bilateral and may be asymmetric. n M  ajor determinant of thickness of pleural plaques is duration from first exposure. n P  leural plaques are usually limited to the parietal pleura. n A  sbestos fibers transported to pleural surface along lymphatic channels and/or by direct penetration result in pleural inflammation and fibrosis.

CLINICAL PRESENTATION

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

n U  sually

n P  leural

n P  leural

first seen 20-30 years after exposure plaques do not cause any symptoms

DIFFERENTIAL DIAGNOSIS n P  revious

tuberculosis trauma n P  revious hemothorax n P  revious

plaques are the most common manifestation of asbestos exposure and invariably are bilateral. n P  revalence of patients with asbestos-related pulmonary and pleural complications has been increasing. n S  ymptoms are usually first seen 20-30 years after exposure. n T  en percent to 15% of pleural plaques calcify; calcification is seldom evident until >30 years after exposure.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Latency



n Most



488

time for development of pleural plaques is usually 20-30 years. patients who have asbestos-related pleuropulmonary disease are asymptomatic; main symptom is shortness of breath. n Chest radiograph has an important role in detection of asbestos-related pleural and parenchymal ­abnormalities and assessment of progression of disease. n Radiograph is falsely negative in 20%-50% of patients with pleural plaques. n High-resolution CT is superior to radiography in detection of pleural plaques. n Asbestos-related pleural disease can be seen in 95%-100% of patients who have evidence of asbestosis on high-resolution CT. n Isolated plaques and diffuse pleural thickening are also seen in tuberculosis, trauma, and hemothorax.

ASBESTOS-RELATED DISEASE

Figure 1.  Pleural plaques. Posteroanterior chest radiograph shows multiple focal pleural-based opacities along the chest wall (straight arrows) and diaphragm (curved arrows) characteristic of pleural plaques. The patient was a 51-year-old shipyard worker.

Figure 3.  Pleural plaques. High-resolution CT image shows characteristic appearance of pleural plaques as sharply circumscribed focal areas of pleural thickening (arrows) separated from the underlying ribs and extrapleural soft tissues by a thin layer of fat.

Asbestos-Related Pleural Plaques    489

Figure 2.  Calcified pleural plaques. Posteroanterior chest radiograph shows numerous bilateral calcified pleural plaques. The patient was an 82-year-old man who had worked for many years in a shipyard.

Figure 4.  Diaphragmatic and costal pleural plaques. Highresolution CT image shows parietal pleural plaques along the intercostal spaces and paravertebral region (arrows) and along the right hemidiaphragm (arrowheads). (Courtesy of Dr. Jorge Kavakama, São Paulo, Brazil.)

Suggested Readings Chapman SJ, Cookson WO, Musk AW, Lee YC: Benign asbestos pleural diseases. Curr Opin Pulm Med 9:266-271, 2003. Cugell DW, Kamp DW: Asbestos and the pleura: A review. Chest 125:1103-1117, 2004.

Roach HD, Davies GJ, Attanoos R, et al: Asbestos: When the dust settles: An imaging review of asbestos-related disease. RadioGraphics 22(Spec No):S167-S184, 2002.

Asbestos-Related Diffuse Pleural Thickening DEFINITION: Asbestos-related pleural disease results from pleural inflammation and fibrosis ­extending into the visceral pleura.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  mooth,

Findings

n S  mooth,

uninterrupted pleural density extends over at least a fourth of the chest wall on radiography. n T  here is a generalized, more or less uniform increase in pleural width. n P  leural thickening is diffuse only in presence of, and in continuity with, an obliterated costophrenic angle. n F  ibrous strands (“crow’s feet”) extending into parenchyma are associated. n B  oth circumscribed and diffuse pleural thickening may be present in same hemithorax. Utility

n U  sed

with pulmonary function tests for monitoring every 3-5 years to identify onset of asbestos-related disease. n L  imited accuracy in distinguishing pleural thickening from extrapleural fat.

CT

uninterrupted pleural density extending over at least a fourth of the chest wall on radiography n S  heet of thickened pleura at least 5 cm in lateral dimension and 8 cm in craniocaudal dimension n I n continuity with obliteration of costophrenic angle n T  ypically spares the mediastinal pleura

CLINICAL PRESENTATION n P  atients

asymptomatic or present with dyspnea lung function with reduction in vital capacity, with or without associated dyspnea n L  atency period of 10-40 years or more n R  estrictive

DIFFERENTIAL DIAGNOSIS n M  alignant

Findings n S  heet

of thickened pleura at least 5 cm in lateral dimension and 8 cm in craniocaudal dimension. n C  onsidered diffuse only in presence of, and in continuity with, an obliterated costophrenic angle. n M  ay calcify; usually focal but occasionally extensive. n M  argin between area of diffuse pleural thickening and adjacent lung frequently irregular as a result of parenchymal fibrosis. n R  arely involves mediastinal pleura; frequently affects parietal pleura, abutting paravertebral gutters.

Utility

n H  igh-resolution

CT is more sensitive than plain chest radiography or conventional CT. n H  igh-resolution CT allows distinction of pleural thickening from extrapleural fat.

mesothelioma effusion n S  equela of tuberculosis n S  equela of previous trauma n S  equela of previous surgery n P  leural

PATHOLOGY n A  sbestos-related

pleural disease resulting from pleural inflammation and fibrosis extending into the visceral pleura. n D  iffuse pleural thickening: may calcify: usually focal but occasionally extensive. n F  requently develops after benign asbestos-related pleural effusion. n L  ess commonly caused by extension of interstitial fibrosis to visceral pleura, consistent with pleural migration of asbestos fibers.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

490

n Diffuse

pleural thickening is manifested radiologically as generalized, more or less uniform increase in pleural width. n Circumscribed and diffuse pleural thickening may be present in the same hemithorax. n Frequency of diffuse pleural thickening increases with time from first exposure and is believed to be dose related. n Thickening frequently develops after benign asbestos-related pleural effusion. n Presence of pleural effusion or circumferential pleural thickening should raise the possibility of ­mesothelioma. n Isolated plaques and diffuse pleural thickening are also seen in tuberculosis, trauma, and hemothorax.

ASBESTOS-RELATED DISEASE

Figure 1.  Diffuse pleural thickening. Chest radiograph shows diffuse left pleural thickening. The pleural thickening along the lateral chest wall is seen in profile as a broad band of homogenous increased opacity, whereas the thickening along the posterior chest wall is seen en face as a hazy increased opacity over the left lower hemithorax.

Figure 3.  Diffuse pleural thickening. CT image obtained 6 years later in same patient as in Figure 2 shows extensive calcification (arrow) of the diffuse pleural thickening. (Courtesy of Dr. Jorge Kavakama, São Paulo, Brazil.)

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n I n

United States, 8-9 million people have had occupational exposure to asbestos. n D  iffuse pleural thickening occurs in 9%-22% of asbestos-exposed workers with pleural disease. n F  requency increases with time from first exposure and is believed to be dose related.

Asbestos-Related Diffuse Pleural Thickening    491

Figure 2.  Diffuse pleural thickening. CT image in a patient with previous asbestos exposure shows diffuse pleural thickening (straight arrows) on the right and pleural plaques (curved arrows) on the left. (Courtesy of Dr. Jorge Kavakama, São Paulo, Brazil.)

Figure 4.  Diffuse pleural thickening. CT image in a patient with previous asbestos exposure shows diffuse bilateral pleural thickening involving the paravertebral pleura and costal pleura but sparing of the mediastinal pleura. Sparing of the mediastinal pleura is helpful in distinguishing benign from malignant pleural thickening.

Suggested Readings American Thoracic Society: Diagnosis and initial management of nonmalignant diseases related to asbestos. Am J Respir Crit Care Med 170:691-715, 2004. International Labour Office (ILO): Guidelines for the Use of the ILO International Classification of Radiographs of Pneumoconioses. Revised Edition 2000 (2002) International Labour Office: Geneva. (Occupational Safety and Health Series, No. 22). Roach HD, Davies GJ, Attanoos R, et al: Asbestos: When the dust settles: An imaging review of asbestos-related disease. RadioGraphics 22(Spec No):S167-S184, 2002.

Asbestos-Related Parenchymal Disease DEFINITION: Pulmonary abnormalities related to asbestos exposure include asbestosis, rounded ­ateletasis, and lung cancer.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n A  sbestosis:

Findings

n A  sbestosis

is evident as reticular, small irregular opacities; shaggy heart sign may be seen. n R  ounded atelectasis is characterized by rounded pleural-based opacity, loss of volume, and comet tail sign and commonly occurs in middle and lower lung. n O  pacity of rounded atelectasis typically abuts area of pleural thickening or pleural effusion. n R  ounded atelectasis is static or grows very slowly and is distinguished from carcinoma by convergence of bronchovascular markings around edges. Utility

n R  adiography

is performed routinely in the evaluation of patients with suspected asbestosis. n F  inding of asbestosis along with a compatible history of exposure is adequate for diagnosis. n S  ensitivity and specificity are limited in cases of mild fibrosis. n C  hest radiograph is falsely negative in 15%-20% of patients with asbestosis.

CT

Findings

n A  sbestosis:

intralobular linear opacities, irregular interlobular septa thickening, subpleural small rounded or branching opacities, subpleural curvilinear opacities, and parenchymal bands, pleural plaques or diffuse pleural thickening in vast majority of patients; tends to progress over time even after cessation of exposure. n R  ound atelectasis: peripheral round or oval opacity with comet tail sign; acute/obtuse angles; volume loss proportional to size of opacity; abuts pleural thickening; can be unilateral or bilateral; enhances markedly with intravenous administration of a contrast agent. n L  ung cancer: similar manifestations to other non– asbestos-related carcinoma. Utility

n H  igh-resolution

CT allows detection of parenchymal abnormalities not evident on chest radiography.

intralobular linear opacities, irregular interlobular septal thickening, ground-glass opacities; small round subpleural opacities; subpleural curvilinear opacities; parenchymal bands; pleural plaques or diffuse pleural thickening. n R  ound atelectasis: peripheral round opacity, abuts pleural thickening; vessels and bronchi curving toward pleura and parenchymal opacity; volume loss proportional to size of opacity. n A  sbestos-related pleural disease is seen in 95%100% of patients who have evidence of asbestosis on high-resolution CT.

n P  atient

is placed prone during imaging to distinguish dependent opacity due to atelectasis from mild fibrosis in dorsal basal lung regions. n F  indings of early asbestosis are neither sensitive nor specific. n C  ondition is diagnosed with confidence only if parenchymal abnormalities are bilateral, present at multiple levels, and associated with pleural plaques.

CLINICAL PRESENTATION n M  ost

patients are asymptomatic. shortness of breath may occur. n N  onproductive cough may be present. n W  eight loss, anorexia, malaise, cough, and hemoptysis occur in lung cancer. n P  rogressive

DIFFERENTIAL DIAGNOSIS n I diopathic

pulmonary fibrosis interstitial pneumonia

n N  onspecific

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Latency



n Chest



492

time for development of asbestosis is 20-40 years, with that of lung cancer 10-60 years. radiograph has important role in detection of asbestosis and assessment of disease progression; findings appear normal in up to 20% of patients with asbestosis. n High-resolution CT findings of early asbestosis are neither sensitive nor specific. n Asbestosis is diagnosed with reasonable confidence when it is bilateral, present at multiple levels, and associated with pleural plaques and diffuse pleural thickening. n Asbestos-related pleural disease is seen in 95%-100% of patients who have evidence of asbestosis on high-resolution CT. n Lung cancer is most common in patients with radiologic evidence of asbestosis.

ASBESTOS-RELATED DISEASE

Figure 1.  Asbestosis. Chest radiograph shows extensive bilateral reticulation and hazy increased opacity (ground-glass opacities) mainly in the lower lobes. Also note enlargement of the hilar pulmonary arteries consistent with pulmonary arterial hypertension. The patient was a 59-year-old man with end-stage asbestosis confirmed at lung transplantation.

Figure 3.  Asbestosis. High-resolution CT image performed with the patient prone shows bilateral predominantly subpleural intralobular lines and irregular thickening of interlobular septa with associated architectural distortion and mild subpleural honeycombing. Also noted are nondependent ground-glass opacities. The high-resolution CT findings resemble those of idiopathic pulmonary fibrosis. The patient was a 60-year-old man with proven asbestosis.

Asbestos-Related Parenchymal Disease    493

Figure 2.  Asbestosis. High-resolution CT image performed with the patient supine shows bilateral predominantly subpleural intralobular lines and irregular thickening of interlobular septa. Also noted are nondependent ground-glass opacities and architectural distortion in the anterolateral aspect of the left upper lobe. The patient was a 76-year-old man with many years of asbestos exposure as a shipyard worker.

Figure 4.  Subpleural nodules in early asbestos-related lung disease. High-resolution CT image with the patient prone shows small, round (dot-like) subpleural opacities (arrows) and localized traction bronchiectasis (arrowheads). They reflect the earliest pulmonary abnormality seen in association with asbestos exposure, that is, fibrosis in the walls of respiratory bronchioles. (Courtesy of Dr. Jorge Kavakama, São Paulo, Brazil.)

494    Asbestos-Related Parenchymal Disease

PATHOLOGY n A  ppearance

varies from slight interstitial ­collagen increase to complete normal lung architecture ­obliteration, with formation of thick fibrous bands and honeycombing. n M  icroscopic diagnosis of asbestosis determined by evidence of diffuse interstitial fibrosis and asbestos bodies (fibers of asbestos to which lung has added iron-­protein coating).­

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ortality

from asbestosis has increased steadily, with it being now the most frequently recorded pneumoconiosis on death certificates. n I n United States, 8-9 million people have had occupational exposure to asbestos, resulting in 300,000 deaths. n A  sbestosis is seen mainly in asbestos miners and millers, asbestos textile workers, and asbestos insulators. n M  ean latency period for development of carcinoma is 45.8 ± 9.4 years, and mean patient age is 67.6 ± 8.4 years.

ASBESTOS-RELATED DISEASE

n A  sbestos-related

lung cancer likely accounts for 2%-3% of all lung cancer deaths among males in Great Britain.

Suggested Readings Akira M, Yokoyama K, Yamamoto S, et al: Early asbestosis: Evaluation with high-resolution CT. Radiology 178:409-416, 1991. American Thoracic Society: Diagnosis and initial management of nonmalignant diseases related to asbestos. Am J Respir Crit Care Med 170:691-715, 2004. Friedman AC, Fiel SB, Fisher MS, et al: Asbestos-related pleural disease and asbestosis: A comparison of CT and chest radiography. AJR Am J Roentgenol 150:268-275, 1988. Gamsu G, Salmon CJ, Warnock ML, Blanc PD: CT quantification of interstitial fibrosis in patients with asbestosis: A comparison of two methods. AJR Am J Roentgenol 164:63-68, 1995. McHugh K, Blaquiere RM: CT features of rounded atelectasis. AJR Am J Roentgenol 153:257-260, 1989. Ohar J, Sterling DA, Bleecker E, Donohue J: Changing patterns in asbestos-induced lung disease. Chest 125:744-753, 2004. Roach HD, Davies GJ, Attanoos R, et al: Asbestos: When the dust settles: An imaging review of asbestos-related disease. RadioGraphics 22(Spec No):S167-S184, 2002.

Asbestos-Related Neoplastic Complications DEFINITION: Asbestos-related neoplastic complications include lung cancer and mesothelioma. IMAGING

DIAGNOSTIC PEARLS

Radiography

n F  indings

Findings n L  ung

nodule or mass and mediastinal lymphadenopathy n P  leural effusion n U  nilateral sheet-like or lobulated pleural thickening n H  ilar

Utility

n P  lays

important role in detection of asbestos-related pleural and parenchymal abnormalities and in assessment of disease progression. n L  imited accuracy in distinguishing benign from malignant pleural disease.

CT

suggestive of mesothelioma include nodular pleural thickening, mediastinal pleural thickening, circumferential pleural thickening, and interlobar fissure thickening n M  esothelioma should be suspected in patients with history of asbestos exposure and unilateral pleural effusion images and moderately hyperintense on proton density- and T2-weighted images n M  arked enhancement of mesothelioma with gadolinium-based contrast agent on T1-weighted images Utility

Findings n L  ung

nodule or mass n H  ilar and mediastinal lymphadenopathy n O  ccasionally may simulate rounded atelectasis: irregular shape, increased opacity out of proportion for volume loss; no curving of adjacent vessels n P  leural effusion n C  ircumferential pleural thickening n N  odular pleural thickening n M  ediastinal pleural thickening n M  arked enhancement with intravenous contrast n P  leural plaques may or may not be seen Utility n C  T

findings suggestive of mesothelioma include unilateral pleural effusion, nodular pleural thickening, mediastinal pleural thickening, circumferential rind-like pleural thickening, and interlobar fissure thickening.

MRI

n M  RI

has limited value in the assessment of lung cancer. patients with mesothelioma, MRI is usually only performed in cases in which contrast-enhanced CT is contraindicated or when extrapleural infiltration has not been clearly demonstrated on CT.

n I n

Positron Emission Tomography Findings

n P  ositive

uptake on FDG-PET in lung cancer and in mesothelioma n F  alse-positive findings in inflammatory lesions and infection Utility

n M  ain

value is detection of extrathoracic metastases.

CLINICAL PRESENTATION n P  leuritic

Findings n L  ung

nodule or mass and mediastinal lymphadenopathy n P  leural effusion n D  iffuse pleural thickening n M  esothelioma: isointense or slightly hyperintense relative to adjacent chest wall muscle on T1-weighted n H  ilar

chest pain may accompany development of benign asbestos effusion or mesothelioma. n L  atency time for lung cancer is 10 to >60 years (mean, 46 years). n L  atency time for development of mesothelioma is 25-60 years. n S  ymptoms of lung cancer include cough, dyspnea, hemoptysis, weight loss, and chest pain.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Asbestos-related

cancers can occur anywhere in the lungs and be of any cell type, but there is a greater likelihood in the lower lungs. n Risk of mesothelioma is much greater after exposure to amphiboles, particularly crocidolite (blue asbestos) than after exposure to chrysotile (white asbestos). n Chrysotile itself can cause malignant mesothelioma, although the risk is much lower than for amphiboles. n Mesothelioma should be suspected in patients with asbestos exposure and unilateral pleural effusion and/or nodular, mediastinal, or circumferential pleural thickening.

495

496    Asbestos-Related Neoplastic Complications

Figure 1.  Mesothelioma. Chest radiograph demonstrates left nodular and circumferential pleural thickening, with associated volume loss of the left hemithorax, ipsilateral mediastinal shift, and elevation of the hemidiaphragm. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Canada)

ASBESTOS-RELATED DISEASE

Figure 2.  Mesothelioma. Non–contrast-enhanced CT shows nodular, circumferential, and mediastinal (arrows) pleural thickening of right hemithorax, in keeping with biopsy-proven mesothelioma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Canada)

Figure 3.  Mesothelioma. A contrast-enhanced CT demonstrates that the pleural tumor enhances significantly (same patient as in Fig. 2). Mediastinal pleural thickening is seen clearly (arrows). No pleural fluid was present. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Canada)

ASBESTOS-RELATED DISEASE

Asbestos-Related Neoplastic Complications    497

n S  ymptoms

n T  he

of mesothelioma are chest pain, cough, dyspnea, and weight loss.

DIFFERENTIAL DIAGNOSIS n A  sbestos-related

diffuse pleural thickening atelectasis n B  enign pleural effusion n P  leural metastases n R  ound

PATHOLOGY n A  mphiboles,

particularly crocidolite, are more potent than chrysotile in inducing lung cancer. n M  echanism of carcinogenesis is unclear. n A  sbestos-related cancers can occur anywhere in lungs and be of any cell type. n I t is controversial whether asbestos-related lung cancer arises only in the presence of pulmonary fibrosis. n P  athogenesis of mesothelioma remains unclear.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  sbestos

exposure is associated with increased risk of small cell and non–small cell lung carcinoma and mesothelioma.

risk of lung cancer is magnified severalfold in c­ igarette smokers. n A  sbestos-related lung cancer likely accounts for 2%-3% of all lung cancer deaths among men in Great Britain. n N  umber of asbestos-related lung cancers is between two-thirds and one death for every mesothelioma death.

Suggested Readings British Thoracic Society Standards of Care Committee: BTS statement on malignant mesothelioma in the UK, 2007. Thorax 62 (Suppl 2): ii1–ii19, 2007. Hodgson JT, Darnton A: The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure. Ann Occup Hyg 44:565-601, 2000. Robinson BW, Lake RA: Advances in malignant mesothelioma. N Engl J Med 353:1591-1603, 2005. Robinson BW, Musk AW, Lake RA: Malignant mesothelioma. Lancet 366:397-408, 2005. Roggli VL, Sharma A, Butnor KJ, et al: Malignant mesothelioma and occupational exposure to asbestos: A clinicopathological correlation of 1445 cases. Ultrastruct Pathol 26:55-65, 2002.

Part 50 

UNCOMMON PNEUMOCONIOSES

Aluminum Pneumoconiosis DEFINITION: Inhalation of aluminum dust can result in interstitial fibrosis and patchy granulomatous

pneumonitis.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n D  iffuse

Findings

n B  ilateral

hazy opacities or small nodular opacities more pronounced in upper or middle zones n R  eticulation and honeycombing (sometimes diffuse) Utility

n R  adiography

is main imaging modality used in initial assessment and follow-up of patients. n C  hest findings become apparent after few months or several years of exposure.

CT

interstitial fibrosis severe in upper lung zones, although it may be diffuse n C  entrilobular nodules, bilateral reticulation, and ground-glass opacities n E  xposure to aluminum dust and pot room fumes n M  ost

n H  ypersensitivity n D  rug-induced

pneumonitis lung disease

PATHOLOGY

Findings

n W  ell-defined

nodules of 2-5 mm in diameter or illdefined centrilobular nodules diffusely throughout both lungs n S  mall ill-defined, rounded, centrilobular opacities mainly in upper lobes in early stages n F  ibrosis, resulting in reticular pattern and honey­combing n G  round-glass opacities with or without traction bronchiectasis n I ncreased attenuation of mediastinal lymph nodes Utility

n H  igher

sensitivity and specificity show abnormalities in patients with normal radiograph

n M  ay

CLINICAL PRESENTATION n C  ough

and dyspnea on exertion pneumothorax n P  ulmonary function test results consistent with reduced lung volumes and decreased transfer factor (DLco) n S  pontaneous

DIFFERENTIAL DIAGNOSIS n N  onspecific

interstitial pneumonia pulmonary fibrosis n S  arcoidosis n I diopathic

n S  tearin-coated,

mineral oil–coated, and bare aluminum metal may be all equally effective in producing fibrosis. n S  ubpleural and interstitial fibrosis occurs with scar emphysema and spotted granulomatous pneumonitis with giant cells. n H  istologic examination shows interstitial fibrosis, typically most severe in upper lobes, and patchy granulomatous pneumonitis with giant cells. n H  igh interstitial concentrations of aluminum are found. n D  esquamative interstitial pneumonia, granulomatous lung reaction, and pulmonary alveolar proteinosis have been described after exposure to fumes from aluminum welding.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  luminum

pneumoconiosis is rare, although exposure to aluminum is very common. n S  mall irregular opacities were observed in 7%-8% of 788 male employees of one aluminum production company. n P  revalence is 2 cm in postpneumonectomy space: sensitive indicator of bronchopleural fistula. n O  ther indicators of bronchopleural fistula: new airfluid level and expansion of loculated pleural air collection in postresection residual space n A  bnormal increase in the amount of fluid in the postpneumonectomy space suggests hemothorax or empyema n L  ung herniation: often not visible on frontal chest radiograph but appears as retrosternal lucency on lateral chest radiograph n L  obar torsion: lobar atelectasis (earliest finding), lobar congestion (rapidly expanding consolidation/mass in affected lobe, hilar shift away from affected side) Utility

n R  adiography

has low diagnostic accuracy in detection of postoperative complications.

CT

Findings

n B  ronchopleural

fistula: direct connection between central bronchus and pleura, parietal pleura enhancement after contrast, effacement of extrapleural fat. n P  ostpneumonectomy syndrome: marked rightward, posterior displacement of mediastinum; counterclockwise rotation of heart and great vessels; and left lung hyperinflation and herniation; narrowing of bronchus. n L  obar torsion: increased volume and consolidation and decreased attenuation because of poor arterial flow.

fistula: direct connection between central bronchus and pleura, parietal pleura enhancement after administration of a contrast agent, effacement of extrapleural fat. n P  ostpneumonectomy syndrome: marked rightward, posterior displacement of mediastinum; counterclockwise rotation of heart and great vessels; and left lung hyperinflation and herniation. n L  obar torsion: increased volume and consolidation and decreased attenuation because of poor arterial flow. n S  ensitive indicator of bronchopleural fistula: decrease in air-fluid level >2 cm in postpneumonectomy space. n A  dditional

findings of lobar torsion: tapering/obliteration of proximal pulmonary artery and associated bronchus and ground-glass attenuation in affected lobe.

Utility n C  T

is best diagnostic technique to identify the pathologic process underlying abnormal mediastinal shifts.

CLINICAL PRESENTATION n C  hest

pain, fever, cough, dyspnea

PATHOLOGY n W  ound

infection occurs with increased frequency in chest wall reconstructions because prosthetic mesh is an excellent substrate for bacterial growth. n A  bnormal mediastinal shifts may be caused by restrictive or expansile lung process. n R  isk factors for bronchopleural fistula include inflammatory disease, preoperative irradiation, and resection involving the right lung.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

560

n Common

complications after thoracotomy include hemorrhage at the surgical site, infection, and ­ ronchopleural fistula. b n Bronchopleural fistula typically occurs within the first 2 weeks postoperatively. n Postpneumonectomy syndrome typically occurs in children and young adults months to years after ­pneumonectomy and results in progressive narrowing of the contralateral main bronchus.

POSTOPERATIVE COMPLICATIONS

Thoracotomy (Including Pneumonectomy and Lobectomy)    561

Figure 1.  Postpneumonectomy course complicated by empyema. Three days after left pneumonectomy, the amount of fluid that has accumulated, the position of the left hemidiaphragm (arrowheads), and the shift of the tracheal air column to the left (open arrows) are all consistent with a normal postoperative course. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 3.  Postpneumonectomy syndrome. CT scan performed at end inspiration shows narrowing of the left lower lobe bronchus (arrow). (Case courtesy of Dr. Fred Matzinger, Department of Radiology, The Ottawa Civic Hospital, Ottawa, Canada. From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 2.  Postpneumonectomy course complicated by empyema. At 7 days, the left hemidiaphragm (arrowheads) has undergone some depression and the tracheal air column (open arrows) has returned to the midline. Such a change should suggest empyema, bronchopleural fistula, pleural hemorrhage, or (possibly) chylothorax. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 4.  Postpneumonectomy syndrome. Expiratory CT scan shows decreased attenuation and vascularity in the left lower lobe as a result of air trapping. (Case courtesy of Dr. Fred Matzinger, Department of Radiology, The Ottawa Civic Hospital, Ottawa, Canada. From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

562    Thoracotomy (Including Pneumonectomy and Lobectomy)

n P  ostpneumonectomy

syndrome results in compression of nonoperative main-stem bronchus leading to airway narrowing. n L  obar torsion may result in pulmonary infarction and death; bronchial compression results in lobar atelectasis, and arterial compression causes lobar congestion.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n W  ound

infection occurs in almost 5% of chest wall reconstructions. n O  nly one third of postpneumonectomy patients have complete pleural fluid resorption. n S  tump thrombosis occurs in approximately 10% of postoperative cases and is more common in the right pulmonary artery stump. n B  ronchopleural fistula incidence after pulmonary resection occurs in 5%-8%, 3%-6%, and 0.5%-1.0% after extrapleural pneumonectomy, pneumonectomy, and lobectomy, respectively.

POSTOPERATIVE COMPLICATIONS

n P  ostpneumonectomy

syndrome almost exclusively follows right pneumonectomy and typically occurs in children and young adults months to years after pneumonectomy. n L  obar torsion is uncommon.

Suggested Readings Attili A, Kazerooni E: Postoperative cardiopulmonary thoracic imaging. Radiol Clin North Am 42:543-564, 2004. Kim EA, Lee KS, Shim YM, et al: Radiographic and CT findings in complications following pulmonary resection. RadioGraphics 22:67-86, 2002. Kim SH, Lee KS, Shim YM, et al: Esophageal resection: Indications, techniques, and radiologic assessment. RadioGraphics 21:11191137, 2001. Konen E, Yellin A, Greenberg I, et al: Complications of tracheal and thoracic surgery: The role of multisection helical CT and computerized reformations. Clin Radiol 58:341-350, 2003.

Cardiovascular Surgery DEFINITION: Complications can occur after coronary artery bypass grafting (CABG), cardiopulmonary bypass, aortic aneurysm repair, and aortic dissection surgery. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  aphenous

Findings

n S  aphenous

vein graft aneurysm connecting to left anterior descending or left circumflex coronary artery: left upper cardiac border masses n S  aphenous graft aneurysm connecting to right coro­ nary artery and left anterior descending artery: soft tis­ sue at right and left lower cardiac borders n P  neumopericardium: sharp outline of air contouring some or all of the heart n H  emopericardium/pericardial effusion: loss of mediasti­ nal contour detail, widened subcarinal angle, “differential density sign,” increased pericardial stripe size >2 mm n P  ostpericardiotomy syndrome: most commonly pre­ sents as concomitant pericardial and bilateral pleural effusions, often with basilar opacities n A  ortic stent-graft complications: migration, kinking, and fracture; aortic perforation (rapidly enlarging peri­ aortic hematoma or hemothorax) n P  ost CABG: edema and bleeding (widened cardiomediasti­ nal silhouette with loss of contour details), interstitial edema n B  y third postoperative day: pulmonary edema begin­ ning to resolve and cardiomediastinal silhouette begin­ ning to return to its preoperative appearance n S  mall pericardial effusion, pleural effusions, and atel­ ectasis (commonly left sided): common in early post­ operative period, often persists for weeks n T  ransient phrenic nerve paresis (temporary hemi­ diaphragm elevation) may occur after cardiopul­ monary bypass hypothermia with local ice-slush application Utility

n P  erformed n H  elpful

routinely in detecting most postoperative complications

CT

Findings n P  artial

saphenous vein graft occlusion: vessel nar­ rowing (from thrombosis, atherosclerotic plaque); complete occlusion: contrast within proximal graft seg­ ment, total graft absence

vein graft aneurysm: enhancing, round mass connected to graft lumen that contains variable amount of thrombus causing occlusion n C  onstrictive pericarditis: pericardial calcification, narrowed tubular right ventricle, sigmoid-shaped ventricular septum, pericardial thickening ≥4 mm (hallmark sign) n P  seudoaneurysm: enhancing outpouching from aortic anastomotic site, low-attenuation component (thrombosis); infected pseudoaneurysm demonstrating septa and fluid collections n G  raft infection: perigraft air; expanding, irregular, septated perigraft fluid/high-attenuation soft tissue; loss of perigraft fat attenuation n E  ndoleak: appearance of contrast inside aneurysmal sac n E  nlarged pericardial space (>2 mm) with water or blood attenuation for pericardial effusion and hemopericardium, respectively n P  ostpericardiotomy syndrome: most commonly presents as concomitant pericardial and bilateral pleural effusions, often with basilar opacities

n S  aphenous

vein graft aneurysm: enhancing, round mass connected to graft lumen that contains variable amount of thrombus n E  nlarged pericardial space (>2 mm) with water or blood attenuation for pericardial effusion and hemo­ pericardium, respectively n C  onstrictive pericarditis: pericardial calcification, nar­ rowed tubular right ventricle, sigmoid-shaped ventricular septum, pericardial thickening >4 mm (hallmark sign) n P  seudoaneurysm: enhancing outpouching from aortic anastomotic site, low-attenuation component (throm­ bosis); infected pseudoaneurysm demonstrating septa and fluid collections n T  hrombotic graft occlusion: intraluminal low-­attenuation mass; perigraft hematoma: homogeneous low-­density collection, sharp margins, lacking septa and gas

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n G  raft



n N  ormal



infection is a serious complication that can lead to complete graft failure. postoperative changes often mimic a pathologic process. n D  ifferential diagnosis includes early postoperative changes (post-CABG edema and bleeding, interstitial edema, atelectasis, small pericardial/pleural effusions, perigraft air/fluid collections). n S  ite of coronary artery reattachment to the graft often demonstrates contrast-enhancing bulge that can mimic a pseudoaneurysm.

563

564    Cardiovascular Surgery

Figure 1.  Saphenous vein graft aneurysm in a 69-year-old man 2 years after coronary bypass graft surgery. Contrastenhanced chest CT shows dilatation and thrombosis in the proximal part of saphenous vein graft consistent with graft aneurysm (arrow). (Courtesy of Dr. Charles S. White, University of Maryland, Baltimore)

POSTOPERATIVE COMPLICATIONS

Figure 2.  Synthetic graft infection in a 42-year-old man after placement of a graft for aortic dissection. Contrast-enhanced chest CT shows air and fluid anterior and lateral to ascending aorta consistent with a graft infection (arrow). Note also residual intimal flap in proximal descending aorta (arrowhead). (Courtesy of Dr. Charles S. White, University of Maryland, Baltimore)

Figure 3.  Endoleak. A 78-year-old man with stent-graft for aortic aneurysm repair presented with endoleak. Contrast-enhanced chest CT demonstrates a metallic stent with adjacent contrast extravasation and hematoma (arrow). (Courtesy of Dr. Charles S. White, University of Maryland, Baltimore)

Cardiovascular Surgery    565

POSTOPERATIVE COMPLICATIONS

n G  raft

infection: perigraft air; expanding, irregular, sep­ tated perigraft fluid/high attenuation soft tissue; loss of perigraft fat attenuation n E  ndoleak: appearance of contrast medium inside aneu­ rysmal sac Utility

n S  uperior

to radiograph in demonstrating postoperative complications.

Interventional Radiology Utility

n C  atheter

angiography remains gold standard for postCABG graft assessment

CLINICAL PRESENTATION n C  ardiac

tamponade n P  ostpericardiotomy syndrome from 2 weeks to 6 months after pericardiotomy n F  ever, chest pain

PATHOLOGY n C  omplications

after CABG include massive air embo­ lism, sternal wound infection, hemomediastinum, and acute lung injury. n P  ericardial complications after CABG include pneumo­ pericardium, hemopericardium, constrictive pericardi­ tis, and postpericardiotomy syndrome. n P  athologic mediastinal widening is caused by air, blood, and other fluids in pericardial sac; rapid and massive accumulation can cause cardiac tamponade. n P  ostpericardiotomy syndrome is an autoimmunerelated disease occurring 2 weeks to 6 months after pericardiotomy.

n I mportant

complications accompanying use of syn­ thetic aortic grafts and stent-grafts are pseudoan­ eurysm, perigraft hematoma, aortic perforation, endoleak, and graft infection. n A  ortic perforation may occur either during stent-graft insertion or after erosion of aortic wall by stent-graft struts. n E  ndoleak: connection between aneurysm sac and bloodstream through or around stent-graft is caused by stent-graft misplacement, lumen size mismatch, and incomplete expansion.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n S  emicircular

thin thrombi within inner circumference of the stent are seen in up to 19% of cases. n S  aphenous vein graft aneurysm is an infrequent com­ plication after CABG and most common at the site of graft anastomosis. n T  hrombotic graft occlusion is rare.

Suggested Readings Attili A, Kazerooni E: Postoperative cardiopulmonary thoracic imag­ ing. Radiol Clin North Am 42:543-564, 2004. Frazier AA, Qureshi F, Read KM, et al: Coronary artery bypass grafts: Assessment with multidetector CT in the early and late postopera­ tive settings. RadioGraphics 25:881-896, 2005. Garzón G, Fernández-Velilla M, Martí M, et al: Endovascular stent-graft treatment of thoracic aortic disease. RadioGraphics 25(Suppl 1): S229-S244, 2005. Orton DF, LeVeen RF, Saigh JA, et al: Aortic prosthetic graft infec­ tions: Radiologic manifestations and implications for management. RadioGraphics 20:977-993, 2000. Therasse E, Soulez G, Giroux MF, et al: Stent-graft placement for the treatment of thoracic aortic diseases. RadioGraphics 25:157-173, 2005.

Median Sternotomy DEFINITION: Complications of median sternotomy include incisional dehiscence, wound infection, seroma, retrosternal abscess, mediastinitis, sternal osteomyelitis, sternal nonunion, and fistula formation. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  ternal

Findings

n D  ehiscence:

“midsternal stripe” may be identified as midline vertical radiolucency over sternum that may progressively widen over time. n R  eorientation of sternal wires (sternal wire displacement) is identified in patients with dehiscence. n M  ediastinal widening. Utility

n “  Midsternal

stripe” sign is neither sensitive nor specific for dehiscence and occurs in up to 50% of all post-sternotomy patients. n S  ternal wire displacement is identified in 90% of patients with dehiscence, is considered the single best radiologic sign, and offers potential for early detection. n L  imited value in the diagnosis of retrosternal abscess and mediastinitis.

PATHOLOGY

CT

Findings n S  ternal

wire displacement in dehiscence. n P  arasternal soft tissue stranding, sinus tracts, and abscess formation. n L  arge or enlarging retrosternal or mediastinal fluid collection in infection. n H  igh CT numbers (>30 HU) suggest hematoma. Utility

n S  uperior

to the radiograph in demonstrating postoperative complications n U  sed almost routinely in patients with suspected retrosternal abscess or mediastinitis n U  sed to determine sinus tract depth and reveal any mediastinal communication n O  steomyelitis is difficult to differentiate from minor sternal irregularities caused by surgery and may not become fully apparent until reaching an advanced stage.

CLINICAL PRESENTATION n F  ever,

wound

wire displacement is the single best radiologic sign of dehiscence. n N  ormal postoperative findings that may persist for 2-3 weeks after sternotomy include mild presternal and retrosternal soft tissue infiltration with edema fluid and blood, localized hematoma, postincisional bone defect, and mild pericardial thickening or effusion. n S  mall localized collections of air may be present in the immediate postoperative period but usually resolve by 7 days after surgery. n E  nlarging retrosternal or mediastinal fluid collections are suggestive of infection. n C  T or ultrasound-guided needle aspiration can be helpful to determine if a fluid collection is infected.

chest pain, abnormal drainage from surgical

n I nfectious

complications of median sternotomy include retrosternal abscess, mediastinitis, sternal osteomyelitis, sternal nonunion, and fistula formation.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n T  he

incidence of complications after median sternotomy is low (5.18 mmol/L); entity has nothing to do with lymphatic vessels or chyle. n C  ongenital chylothorax is more often due to malformation of thoracic duct than trauma at birth.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  hylothorax

is uncommon. of cases of chylothorax are due to malignancy, particularly lymphoma, and 25% are due to trauma usually discovered after surgery. n O  ther causes include tuberculosis, sarcoidosis, and amyloidosis. n H  alf

n I t

is a well-recognized complication of pleuropulmonary surgeries and the most common congenital pleural effusion (65%).

Suggested Readings Andrews CO, Gora ML: Pleural effusions: Pathophysiology and management. Ann Pharmacother 28:894-903, 1994. English JC, Leslie KO: Pathology of the pleura. Clin Chest Med 27:157180, 2006. Maskell NA, Butland RJ: BTS guidelines for the investigation of a unilateral pleural effusion in adults. Thorax 58(Suppl 2):i8-i17, 2003. Nair SK, Petko M, Hayward MP: Aetiology and management of chylothorax in adults. Eur J Cardiothorac Surg 32:362-369, 2007. Platis IE, Nwogu CE: Chylothorax. Thorac Surg Clin 16:209-214, 2006. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006. Sahn SA: Pleural effusions of extravascular origin. Clin Chest Med 27:285-308, 2006.

Part 58 

BENIGN PLEURAL THICKENING

Benign Pleural Thickening DEFINITION: Benign pleural thickening is fibrosis of the pleura that may be focal or diffuse. IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  lunting

Findings n A  pical

cap shows thickening of pleural line over convexity of thorax and sharply marginated lower border that frequently is tented/undulating; normally thickness is 5 cm wide, 8 cm in height, 3 mm thick n T  ypically located along posterolateral hemithorax n S  eldom involves mediastinal pleura n U  sually is smooth n C  ontinuous

CLINICAL PRESENTATION n O  ften n M  ay

asymptomatic present as dyspnea due to restrictive lung function

DIFFERENTIAL DIAGNOSIS n C  ollagen

CT

vascular disease empyema n P  revious hemothorax n P  revious thoracic surgery n A  sbestos related pleural disease n M  alignant mesothelioma n P  leural metastases n P  revious

Findings n A  pical

cap shows thickening of pleural line over convexity of thorax commonly associated with extrapleural fat that is 3-20 mm thick. n A  pical pneumothorax can outline the apical cap. n P  leural thickening may be focal or diffuse and may be associated with blunting of costophrenic angle. n D  iffuse thickening on CT is commonly defined as a continuous sheet of pleural thickening >5 cm wide, >8 cm in craniocaudal extent, and >3 mm thick. n D  iffuse benign pleural thickening commonly results in ipsilateral volume loss. n D  iffuse benign pleural thickening commonly involves the costal and paravertebral regions but seldom involves the mediastinal pleura. n A  ccumulation of extrapleural fat is commonly present on CT and suggestive of chronic pleural thickening. n C  hronic fibrothorax occasionally may be associated with hypertrophy of adjacent ribs. Utility

n S  uperior

to chest radiography in evaluating for diffuse pleural thickening and distinguishing benign from malignant pleural thickening

PATHOLOGY n I nflammation

of pleural cavity is central to pathogenesis of pleural fibrosis. n D  iffuse pleural thickening results from thickening and fibrosis of visceral pleura with fusion to parietal pleura over a wide area. n I n asbestos exposure, diffuse pleural thickening is usually preceded by benign asbestos-related pleural effusion.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n B  enign

pleural thickening due to fibrosis is the second most common pleural abnormality. n M  ost common causes of pleural fibrosis are collagen vascular diseases, asbestos exposure, and drugs, especially

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Extrapleural



n Diffuse



588

fat may simulate diffuse pleural thickening on the radiograph. pleural thickening is associated with significant restriction to lung function. n Common causes include asbestos exposure, rheumatoid arthritis, hemothorax, tuberculosis, and previous surgery. n Pleural thickening is almost always preceded by an exudative pleural effusion.

BENIGN PLEURAL THICKENING

Figure 1.  Apical caps. Posteroanterior chest radiograph demonstrates biapical pleural thickening (arrows), which has an undulating margin with the lung. This is symmetric bilaterally and measures 5 mm thick, and obliterates the costophrenic sulci. This meets all the International Labour Organization criteria for bilateral diffuse pleural thickening. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 4.  Apical cap and right pneumothorax. Coronal reconstruction of high-resolution CT shows a small right pneumothorax outlining the right apical pleural thickening (arrow). (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Suggested Readings Huggins JT, Sahn SA: Causes and management of pleural fibrosis. Respirology 9:441-447, 2004. Kim JS, Lynch DA: Imaging of nonmalignant occupational lung disease. J Thorac Imaging 17:238-260, 2002. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006.

Part 59 

PLEURAL NEOPLASMS

Fibrous Tumor of the Pleura DEFINITION: Fibrous tumor of the pleura is a collagenous tumor that arises from mesenchymal cells and is often solitary and well defined.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n T  his

Findings n A 

peripheral solitary, smooth-walled, homogeneous rounded nodule or mass is seen. n “  Incomplete border” sign is when tapering margins form obtuse angles with the chest wall or mediastinum resulting in an ill-defined margin en face. n W  hen they are in contiguity with the diaphragm, they may simulate diaphragmatic eventration. n P  edunculated tumors may be mobile, changing in position with respiration or posture. n P  leural effusions, if large enough, may obscure mass. Utility

n M  ain

imaging modality used in initial assessment

is a solitary, well-defined, pleural-based lesion; calcification can occur in 25% of cases. n S  mall lesions enhance homogeneously whereas large lesions enhance heterogeneously. n M  ost are located in the lower hemithorax. n C  lubbing of fingers (hypertrophic osteoarthropathy) can occur in 4%-5% of cases. n S  ymptomatic hypoglycemia is present in 4%-5% of cases and is more common in large tumors. n C  annot

differentiate benign from malignant pleural tumors unless there is local invasion of chest wall or diaphragm

MRI

CT

Findings

Findings n A 

small tumor is typically a noninvasive, lobular, homogeneous, soft tissue mass that abuts the pleural surface and may form obtuse angles. n I f the tumor is large, areas of necrosis, hemorrhage, and cystic changes are typically identified within it. n M  ass effect on adjacent lung or mediastinum is common. n I ntermediate to high attenuation is seen on unenhanced CT scans. n C  ontrast enhancement tends to be intense as a result of the rich vascularization of the tumor. n G  eographic, linear, or focal nonenhancing areas correspond to necrosis, myxoid degeneration, or hemorrhage within the tumor.

Utility n F  or

further evaluation and characterization of pleural lesion

n L  ow

to intermediate signal intensity on T1- and T2-weighted images n H  igh heterogeneous T2-weighted signal intensity thought to relate to necrosis, cystic or myxoid degeneration, vascular structures, and high cellularity n L  ow signal intensity septa n I ntense heterogeneous enhancement after intravenous injection of gadolinium Utility n M  RI

better characterizes fibrous tumors of pleura. and coronal images permit tumor localization within chest and assessment of diaphragm. n W  ith large tumor, MRI is helpful to better define extent and relationship to mediastinum and diaphragm for surgical planning. n M  RI cannot differentiate benign from malignant pleural tumors unless there is local invasion of chest wall or diaphragm. n S  agittal

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

590

n On

CT, the differential diagnosis includes sarcomatoid mesothelioma, sarcoma, as well as epithelioid hemangiopericytoma. n MRI is superior to CT in defining extent of large tumors. n Histologically, differential diagnosis includes spindle cell carcinoma, spindle cell melanoma, sarcomatoid mesothelioma, and primary and metastatic soft tissue neoplasms. n Immunohistochemical studies are helpful in excluding these other tumors. n Four percent to 5% of cases are associated with hypertrophic osteoarthropathy and 4%-5% with symptomatic hypoglycemia.

PLEURAL NEOPLASMS

Fibrous Tumor of the Pleura    591

Figure 2.  Localized fibrous tumor of the pleura. CT image without contrast depicts a small peripheral lesion that has obtuse angles with the pleura. Core needle biopsy confirmed a fibrous tumor of the pleura. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada) Figure 1.  Localized fibrous tumor of the pleura. Posteroanterior chest radiograph demonstrates a large smoothly defined mass in the left upper hemithorax, abutting the pleura laterally. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 3.  Localized malignant fibrous tumor of the pleura. Contrast-enhanced CT demonstrates a large left-sided mass, displacing the mediastinum contralaterally, which contains “geographic” areas of low attenuation (arrows) within a large malignant fibrous tumor of pleura. These areas correspond to necrosis. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 4.  Localized fibrous tumor of the pleura. Cross-sectional MR image shows the tumor to be predominantly of low T2 signal intensity, containing a few high signal areas, which were thought to correspond with high cellularity (thin arrows) and necrosis (thick arrow). (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

592    Fibrous Tumor of the Pleura

CLINICAL PRESENTATION n A  pproximately

50% of patients are symptomatic. frequent symptoms are dyspnea, cough, and chest pain and are present in 40% of patients. n C  lubbing of fingers (hypertrophic osteoarthropathy) occurs in 4%-5% of cases. n S  ymptomatic hypoglycemia is present in 4%-5% of cases and more common with malignant tumors. n O  nce the tumor is removed, symptoms of osteoarthropathy and hypoglycemia resolve. n H  emoptysis and obstructive pneumonitis may rarely be observed, owing to airway obstruction. n M  ost

DIFFERENTIAL DIAGNOSIS n M  alignant

mesothelioma lymphoma n P  leural metastases n L  ung cancer n P  leural sarcoma n P  leural

PATHOLOGY n T  umor

arises from mesenchymal cells; it commonly occurs in pleura but has also been described in other sites (e.g., pericardium, mediastinum). n E  tiology is unknown in vast majority of cases, and most tumors are benign, with about 12% being malignant. n T  umors usually are well circumscribed, with size range from 1-38 cm; most originate in visceral pleura. n S  ome fibrous tumors have been associated with the presence of insulin-like growth factor in tumor and serum.

PLEURAL NEOPLASMS

n T  umors

appear as low-grade neoplasms of variable cellularity; a “patternless pattern” with random intermingling of tumor cells and collagen is common. n S  ixty-five percent to 80% originate in the visceral pleura and 20%-35% from the parietal pleura. n C  alcification occurs in approximately 25% of cases.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n T  his

relatively uncommon neoplasm accounts for 5%-10% of primary tumors of pleura. n P  revalence is approximately 2.8 cases per 100,000 population. n M  en and women are equally affected. n I t may occur in all age groups (range: 5-87 years), with peak incidence in the sixth and seventh decades.

Suggested Readings Bonomo L, Feragalli B, Sacco R, et al: Malignant pleural disease. Eur J Radiol 34:98-118, 2000. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006. Robinson LA: Solitary fibrous tumor of the pleura. Cancer Control 13:264-269, 2006. Rosado-de-Christenson ML, Abbott GF, McAdams HP, et al: From the archives of the AFIP: Localized fibrous tumor of the pleura. RadioGraphics 23:759-783, 2003.

Malignant Mesothelioma DEFINITION: A malignant mesothelioma is a locally aggressive mesothelial tumor of the pleura that invades the chest wall and surrounding structures. IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  ediastinal

Findings n N  ormal

in early disease to complete opacification of hemithorax n U  nilateral sheet-like or lobulated pleural thickening encasing entire lung n V  olume loss of affected hemithorax n N  odular fissural thickening helpful in diagnosing pleural malignant disease n R  ib destruction and pneumothorax occasionally seen n U  nilateral pleural effusion without mediastinal shift or displacement toward or away from affected hemithorax Utility

n U  sually

first imaging modality used

CT

Findings

n U  nilateral

pleural effusion, nodular pleural thickening, thickening of mediastinal pleura, and thickening of interlobar fissure. n E  xtensive pleural thickening, which may encase lung with rind-like appearance. n M  ay start as one or two pleural nodules that later grow in size or number. n P  leural plaques in 10%-50% of patients. n O  bliteration of extrapleural fat planes, invasion of intercostal muscles, displacement of ribs, or bone destruction seen in some patients. n N  odular pericardial thickening or pericardial effusion n A  ttenuation of pleura increased relative to fluid with strong postcontrast enhancement. Utility n C  T

is imaging modality of choice for evaluating mesothelioma.

pleural thickening and nodular and circumferential pleural thickening are suggestive of pleural malignancy on CT. n P  leural plaques are of limited help in distinguishing mesothelioma from metastatic pleural disease. n U  nilateral pleural effusion may be the only finding.

n A  dministration

of contrast agent enables differentiation between thickened pleura and effusions as well as collapsed lung. n C  ontrast-enhanced CT is ideally performed with 60-second delay, enabling optimal pleural and soft tissue enhancement. n U  se of narrow collimation allows for high-quality multiplanar reformatted images, which are helpful in visualizing involvement of interlobar fissure. n C  T helps in differentiation between benign and malignant pleural disease. n I t does not accurately stage local tumor extent.

MRI

Findings

n R  elative

to adjacent chest wall muscle, mesothelioma is isointense or slightly hyperintense on T1-weighted images. n I t is moderately hyperintense on proton-density– weighted and T2-weighted images. n I t enhances avidly after administration of a gadolinium-based contrast agent. n L  oss of normal fat planes, mediastinal fat extension, and tumoral encasement of >50% mediastinal structure circumference suggest tumor invasion.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Suggestive

signs of pleural malignancy on CT include mediastinal pleural thickening and nodular and ­ ircumferential pleural thickening. c n Diagnostic procedure of choice is thoracoscopic surgery (91%-98% sensitivity) or image-guided needle biopsy as an alternative with high diagnostic accuracy. n Overall prognosis is poor, which is related to tumor histology, nodal status, tumor stage, age, performance status, and other comorbidities. n CT, MRI, and PET do not accurately stage local tumor extent; staging is better done surgically, with ­thoracoscopy, mediastinoscopy, and laparotomy. n Mesothelioma has propensity to spread along chest tube tract, thoracoscopy trocars, and surgical incisions. n Diagnostic dilemmas include adenocarcinoma vs. tubopapillary mesothelioma; reactive mesothelial ­hyperplasia vs. early mesothelioma; and desmoplastic mesothelioma vs. pleuritis vs. pleural plaque. n Differential diagnosis includes parapneumonic effusion, empyema, and metastatic disease from another primary tumor (most commonly of the lung or breast).

593

594    Malignant Mesothelioma

Figure 1.  Mesothelioma. Chest radiograph demonstrates left nodular and circumferential pleural thickening, with associated volume loss of the left hemithorax, ipsilateral mediastinal shift, and elevation of the hemidiaphragm. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 3.  Mesothelioma. CT demonstrates circumferential, nodular right pleural thickening, along with contracted right hemithorax. A small pleural effusion is present, distinct from the thickened mediastinal pleura. Calcified pleural plaques (thin arrows) are present. Note mediastinal invasion by tumor (thick arrow). (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

PLEURAL NEOPLASMS

Figure 2.  Mesothelioma. Nonenhanced CT shows nodular, circumferential, and mediastinal (arrows) pleural thickening of right hemithorax, in keeping with biopsy-proven mesothelioma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 4.  Epithelial mesothelioma. Coronal T1-weighted gadolinium-enhanced MR image depicts a loculated pleural effusion surrounded by nodular, enhancing, pleural thickening (white arrows) that extends to the right crus of the hemidiaphragm. Preservation of the fat plane between the crus and the liver (black arrows) is a helpful sign of lack of invasion by this mesothelioma, which was confirmed at surgery. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Malignant Mesothelioma    595

PLEURAL NEOPLASMS

Utility

n O  nly

performed in cases in which contrast-enhanced CT is contraindicated or when CT fails to adequately demonstrate extrapleural infiltration n E  xcellent soft tissue contrast and multiplanar image acquisition, permitting ready assessment of chest wall and diaphragmatic invasion n C  an provide additional staging information n S  ensitivities and specificities equivalent to those of CT in differentiating benign and malignant pleural disease

Ultrasonography Findings n P  leural

effusion nodules

n I ntrapleural

Utility

n U  seful

in identifying pleural pathologic process for image-guided biopsy with reported accuracy of 80% in diagnosing mesothelioma n U  sed for imaged-guided drainage of effusions n U  sed

Positron Emission Tomography Findings

n S  emi-quantitative

measure of metabolic activity of lesion is significantly higher in malignant than in benign pleural diseases. n E  levated glucose metabolism of tumor cells suggests malignancy. n P  leural thickening occurs. Utility

n F  DG-PET

has been used for diagnosis of mesothelioma. distant metastases may be identified, which can preclude unnecessary surgery. n P  ET does not accurately stage local tumor extent but has the ability to detect extrathoracic metastases. n S  ensitivity in pleural thickening is 97%, with positive predictive value of 94%. n U  nsuspected

CLINICAL PRESENTATION n M  ost

common first symptoms are dyspnea and chest pain, which is often vague, typically nonpleuritic, and may be referred to shoulder. n O  nset is often insidious; as disease progresses the patient may develop dry cough, fever, fatigue, and weight loss. n T  umor may be asymptomatic, with presence of pleural effusion noted incidentally on physical examination or by chest radiography. n P  hysical examination reveals finger clubbing; retraction and dullness on percussion of chest are common. n L  atency period is 35 to 40 years from time of exposure to development of mesothelioma.

DIFFERENTIAL DIAGNOSIS n B  enign

pleural effusion metastases n P  leural lymphoma n F  ibrous tumor of the pleura n B  enign pleural thickening n P  leural

n A  sbestos-related n L  ung

diffuse pleural thickening cancer: Adenocarcinoma

PATHOLOGY n M  alignant

mesothelioma develops in parietal pleura first, then spreads to visceral pleura, chest wall, mediastinum, diaphragm, and abdomen. n I t is usually due to the carcinogenic effect of asbestos via industrial or environmental exposure and classified into epithelial, sarcomatous, mixed epithelial and sarcomatous mesotheliomas. n E  pithelial forms are composed only of polygonal, rounded, cuboidal, or flattened epithelial cells arranged in papillary formations, sheets, or tubules. n S  arcomatous mesotheliomas are usually composed of spindle cells, which may be relatively bland or high grade. n D  esmoplastic mesothelioma is a variant of sarcomatous mesothelioma in which malignant cells are embedded in a dense collagenous matrix. n M  ixed epithelial and sarcomatous mesotheliomas can show any combination of patterns seen in either form.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n I ncidence

has markedly increased in the past few decades in North America, Europe, the United States, Israel, New Zealand, Japan, and Denmark. n T  here are 2000-3000 new cases per year reported in the United States. n T  hese tumors account for an estimated 20 deaths per million males per year in North America and Europe. n E  pithelial type is most common (50%-60%), then sarcomatous (35%) and mixed (15%) forms. n B  oth men and women are affected, but overall incidence is much higher in men. n M  ean age at diagnosis is 63 years, with only 2%-5% estimated to appear in childhood or adolescence. n S  ex predominance is largely related to occupational asbestos exposure; at highest risk are plumbers, pipe fitters, and sheet-metal workers. n R  isk increases with prior radiation and chronic inflammation such as tuberculosis; simian virus SV40 association is estimated to account for 10%-20% of mesotheliomas.

Suggested Readings Bonomo L, Feragalli B, Sacco R, et al: Malignant pleural disease. Eur J Radiol 34:98-118, 2000. British Thoracic Society Standards of Care Committee: BTS statement on malignant mesothelioma in the UK, 2007. Thorax 62(Suppl 2): ii1-ii19, 2007. Pistolesi M, Rusthoven J: Malignant pleural mesothelioma: Update, current management, and newer therapeutic strategies. Chest 126:1318-1329, 2004. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006. Wang ZJ, Reddy GP, Gotway MB, et al: Malignant pleural mesothelioma: Evaluation with CT, MR imaging, and PET. RadioGraphics 24:105-119, 2004. Yamamuro M, Gerbaudo VH, Gill RR, et al: Morphologic and functional imaging of malignant pleural mesothelioma. Eur J Radiol 64:356-366, 2007.

Pleural and Extrapleural Lipoma DEFINITION: A lipoma is a benign soft tissue neoplasm of pleura that likely arises from submesothelial mesenchymal cells and has characteristic uniform fat density. IMAGING

DIAGNOSTIC PEARLS

Radiography

n T  umor

Findings n T  ends

to have tapered margins and form an obtuse angle with the chest wall and to have poorly defined margins when seen en face.

Utility

n A  bnormality

commonly seen incidentally on chest radiograph n L  imited value in differential diagnosis from other pleural or chest wall tumors

CT

Findings Utility

n A  llows

DIFFERENTIAL DIAGNOSIS n F  ibrous

tumor of the pleura tumor n E  xtrapleural fat n N  eurogenic

n U  niform

units).

with uniform fat density (−50 to −120 Hounsfield units) on CT. n S  moothly marginated lesion of signal intensity similar to subcutaneuous fat on MR. n N  o enhancement after contrast agent administration.

fat density (−50 to −120 Hounsfield

confident diagnosis of lipoma

MRI

Findings

n B  enign

soft tissue neoplasm of pleura that likely arises from submesothelial mesenchymal cells

n M  ass n H  as

tion.

with similar intensity to subcutaneous fat. no enhancement after contrast agent administra-

PATHOLOGY

Utility

n A  llows

confident diagnosis of lipoma

CLINICAL PRESENTATION n U  sually

asymptomatic

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n B  enign

lipoma is the most common soft tissue neoplasm of the pleura.

Suggested Reading Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Pleural



n The

596

lipomas are benign tumors usually found incidentally on the chest radiograph or CT. CT findings are usually diagnostic.

PLEURAL NEOPLASMS

Figure 1.  Pleural lipoma. Magnified view of the left upper lobe from a frontal chest radiograph shows a nodular opacity with tapered margins (arrows) that forms an obtuse angle with the chest wall. Note that the medial margins of the nodule are well defined, indicating contact with lung, whereas the outer margins are poorly defined, indicating contact with the pleura and chest wall.

Figure 3.  Pleural lipoma. Axial nonenhanced CT shows a pleural-based homogeneous fat attenuation lesion (arrow), consistent with a benign pleural lipoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Pleural and Extrapleural Lipoma    597

Figure 2.  Pleural lipoma. Magnified view from a CT scan shows pleural and chest wall mass with homogeneous fat attenuation characteristic of lipoma (arrow). The patient was a 55-year-old man.

Figure 4.  Pleural lipoma. Coronal, fat-saturated, T1-weighted MRI after gadolinium injection shows the lesion to be of low signal (fat suppressed) with no evidence of contrast enhancement. This is consistent with an incidental benign pleural lipoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Pleural Lymphoma DEFINITION: A pleural lymphoma is a malignant proliferation of lymphocytes involving the pleura. IMAGING

DIAGNOSTIC PEARLS

Radiography

n U  nilateral

Findings n P  leural n F  ocal

Utility

effusion or diffuse, smooth or nodular pleural thickening

n U  sually

first imaging modality used for assessment

CT

or bilateral pleural effusion, with or without pleural thickening n F  ocal or diffuse or nodular or smooth pleural thickening n P  osterior mediastinal lymphadenopathy n P  leural involvement usually associated with disseminated disease n I ncreased uptake on FDG-PET imaging

Findings n P  leural

effusion or diffuse, smooth or nodular pleural thickening n M  ediastinal and retrocrural lymphadenopathy common

n A  fter

Utility

DIFFERENTIAL DIAGNOSIS

n F  ocal

n C  T

is superior to radiography in demonstrating pleural effusion and pleural thickening.

MRI

Findings n P  leural n F  ocal

Utility

effusion or diffuse, smooth or nodular pleural thickening

n C  omparable

to CT for assessment of pleural lymphoma but seldom utilized in clinical practice n H  elpful in patients with contraindication to intravenous ionic contrast material

PET

Findings

n I ncreased

Utility

uptake of FDG

n P  ET

and PET/CT can be helpful in distinguishing lymphoma from benign pleural thickening. n P  ET is superior to CT in the staging of lymphoma.

CLINICAL PRESENTATION n C  hest n C  hest

pain and fever wall swelling

tumor invasion of spinal cord, paralysis of lower limbs possible presenting feature n U  sually occurs as part of disseminated disease

n M  alignant

mesothelioma metastases n B  enign pleural thickening n B  enign pleural effusion n P  leural

PATHOLOGY n L  ymphomatous

deposits arise from lymphatic channels and lymphoid aggregates in subpleural connective tissue below visceral pleura. n P  leural involvement occurs in both Hodgkin and nonHodgkin lymphoma.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n L  ymphoma constitutes 10% of secondary pleural tumors. n A  pproximately

10% of malignant effusions are caused by pleural lymphoma. n P  revalence of pleural disease in lymphoma is reported to be 26%-31%. n P  leural lymphoma occurs in conjunction with mediastinal lymphadenopathy (70%) but may occur as extension of pulmonary lymphoma.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

598

n Secondary

tumors account for about 90% of pleural neoplasms; they include metastases, lymphoma, and uncommon tumors such as thymoma. n Approximately 80% of all malignant pleural effusions are caused by metastatic tumor from lung, breast, ovary, stomach, or lymphoma. n Lymphoma constitutes 10% of secondary pleural tumors. n Approximately 10% of malignant effusions are caused by pleural lymphoma. n Prevalence of pleural disease in lymphoma is reported to be 26%-31%. n Pleural lymphoma usually occurs as part of disseminated disease and most commonly in association with mediastinal lymphadenopathy. n CT and PET are helpful in distinguishing benign from malignant pleural thickening.

PLEURAL NEOPLASMS

Figure 1.  Lymphoma. CT image demonstrates thick, nodular, circumferential pleural thickening in the apical right hemithorax (arrow). (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 3.  Lymphoma. Contrast-enhanced CT demonstrates a large enhancing periaortic mass that is contiguous with a smooth area of parietal pleural thickening (arrow) in the left hemithorax. Bilateral pleural effusions are present, typical for pleural involvement with lymphoma. The patient also had extensive retroperitoneal lymphadenopathy (not shown), and biopsy of the retrocrural mass was consistent with diffuse B-cell lymphoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Pleural Lymphoma    599

Figure 2.  Lymphoma. CT image at the level of the lower hemithorax shows more nodular pleural thickening (arrows) in association with a large pleural effusion and right lower lobe atelectasis. The patient did not present with adenopathy elsewhere in the body, and biopsy of the pleural thickening was diagnostic for diffuse B-cell lymphoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 4.  Non-Hodgkin lymphoma. Contrast-enhanced CT demonstrates smooth pleural thickening, contiguous with the retrocrural (long arrow) and posterior mediastinal lymphadenopathy (short arrow). The patient was known to have disseminated B-cell lymphoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Suggested Readings Bonomo L, Ciccotosto C, Guidotti A, et al: Staging of thoracic lymphoma by radiological imaging. Eur Radiol 7:1179-1189, 1997. Bonomo L, Feragalli B, Sacco R, et al: Malignant pleural disease. Eur J Radiol 34:98-118, 2000.

English JC, Leslie KO: Pathology of the pleura. Clin Chest Med 27:157-180, 2006. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006.

Pleural Metastases DEFINITION: Metastases to the pleura occur most commonly in carcinoma of the lung, breast, ovary,

and stomach.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  leural

Findings n P  leural

effusion n F  ocal or diffuse, smooth or nodular pleural thickening Utility

n U  sually

n L  imited

first imaging modality value in the diagnosis of pleural metastases

CT

Findings

effusion pleural thickening, nodular pleural thickening, pleural nodule or mass, circumferential pleural thickening, and extension into adjacent soft tissues

effusion

n C  ircumferential

pleural thickening pleural thickening n M  alignant pleural effusion shown by increased uptake on FDG-PET n B  ronchogenic carcinoma, breast cancer, lymphoma, and ovarian and gastric carcinoma account for the majority of metastases to the pleura. n N  odular

n P  leural

n M  ediastinal

Utility

n S  uperior

to radiography in demonstrating pleural effusion and findings suggestive of pleural metastases

n A  denocarcinoma

of the lung involves the pleura because of its peripheral nature and its propensity to invade the vasculature. n M  etastatic carcinomas often have elevated levels of carcinoembryonic antigen.

Positron Emission Tomography Findings

n I ncreased

FDG uptake

Utility

n H  elpful

in distinguishing benign from malignant pleural effusion and thickening

CLINICAL PRESENTATION n D  yspnea,

pleuritic chest pain, weight loss, malaise

DIFFERENTIAL DIAGNOSIS n M  alignant

mesothelioma lymphoma n B  enign pleural effusion n B  enign pleural thickening n P  leural

PATHOLOGY n M  echanism

is most often contiguous spread and invasion of tumor into pulmonary vasculature and lymphatics. n I nvasive thymoma can involve the pleura in a contiguous manner or with “drop metastases.”

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  pproximately

80% of all malignant pleural effusions are caused by metastatic tumor from lung, breast, ovary, stomach, or lymphoma. n A  denocarcinoma of the lung is most common cell type to involve the pleura. n S  econdary tumors account for about 90% of pleural neoplasms; they include metastases, lymphoma, and uncommon tumors such as thymoma. n A  pproximately 25% of pleural effusions in older patients are malignant in origin. n M  ost pleural metastases involve visceral pleura.

Suggested Readings Aquino SL: Imaging of metastatic disease to the thorax. Radiol Clin North Am 43:481-495, 2005:vii. Bonomo L, Feragalli B, Sacco R, et al: Malignant pleural disease. Eur J Radiol 34:98-118, 2000. English JC, Leslie KO: Pathology of the pleura. Clin Chest Med 27(2):157-180, 2006. Qureshi NR, Gleeson FV: Imaging of pleural disease. Clin Chest Med 27:193-213, 2006.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n CT,



n It

600

MRI, and PET are helpful in distinguishing benign from malignant pleural thickening. is often impossible radiologically to differentiate pleural metastases from mesothelioma.

PLEURAL NEOPLASMS

Pleural Metastases    601

Figure 1.  Metastatic breast carcinoma. CT image demonstrates nodular pleural thickening that involves the major fissure (arrows). The patient had a prior right mastectomy for breast cancer. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 2.  Metastatic breast carcinoma. Mediastinal windows show the enhancing parietal pleural thickening (thick arrow) and extension of pleural metastases into the anterior cardiophrenic angle (thin arrow). (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 3.  Thymoma pleural metastases. CT image shows two pleural nodules (arrows) in the major fissure in a man with prior sternotomy for resection of invasive thymoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Figure 4.  Thymoma pleural metastases. CT image at the level of the hemidiaphragm demonstrates a larger “drop metastasis” (arrow), which is pleural seeding from a thymoma. (Courtesy of Dr. Jean M. Seely, University of Ottawa, Ottawa, Canada)

Pneumomediastinum DEFINITION: Pneumomediastinum refers to the presence of air or other gas in the mediastinal space. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  treaks

Findings

n I ncrease

in depth and lucency of retrosternal space in adults n G  ray-black density streaks separating portions of mediastinal pleura from contents n F  ocal bubble-like/larger gas collections outlining mediastinal structures n V  ertical streaks of radiolucency adjacent within lateral borders of mediastinal shadow n L  oculated mediastinal air appearing as rounded hyperlucent cystic lesion adjacent/overlying mediastinum n C  ontinuous diaphragm sign n V  sign of Naclerio, ring-around-the-artery sign, thymic spinnaker-sail sign Utility

n O  ften

first imaging modality to show presence of pneumomediastinum n H  elpful in initial assessment and follow-up n L  ateral view more useful in showing streak-like areas produced by mediastinal air; may also identify pneumomediastinum not evident on a frontal view

CT

of gray-black density separating portions of mediastinal pleura from mediastinal contents n F  ocal bubble-like or larger collections of gas outlining the mediastinal structures n R  ounded hyperlucent paramediastinal lesions (loculated pneumomediastinum) n C  ontinuous diaphragm sign, V sign of Naclerio, ring-around-the artery sign, thymic spinnaker-sail sign

CLINICAL PRESENTATION n M  ay

be asymptomatic or may present as variable degrees of chest discomfort n R  etrosternal chest pain aggravated by breathing and position changes, dyspnea, shortness of breath, dysphagia, and weakness n T  ension pneumomediastinum: acute diastolic dysfunction, cardiac tamponade, impaired venous return to heart, and airway distortion impeding air flow

DIFFERENTIAL DIAGNOSIS

Findings

n A  bnormal

air collections within the various mediastinal compartments n A  bnormal air collections due to ruptured alveoli associated with acute respiratory distress syndrome/pulmonary fibrosis easily recognized on CT n P  ulmonary laceration in blunt chest trauma n P  eriesophageal fluid and air collections suggestive of esophageal rupture Utility

n S  uperior

to radiography in demonstrating presence of pneumomediastinum and underlying cause

n M  ach

effect

n P  neumothorax

n P  neumopericardium

PATHOLOGY n T  hree-step

pathophysiologic process (Macklin effect): traumatic alveolar rupture, air dissection along bronchovascular sheaths, and spread of pulmonary interstitial emphysema into mediastinum

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Diagnosis



n Radiographic



604

of pneumomediastinum is made by chest radiography in most cases. distinction between pneumomediastinum and pneumopericardium is that pneumopericardium does not extend above aortic arch or into superior mediastinum. n Clinical correlation is essential and dictates further evaluation and type of examination needed. n Main conditions to exclude are trauma, mediastinitis, and perforated esophagus. n Boerhaave syndrome is considered in a patient with history of vomiting followed by chest pain and pneumomediastinum. n Patients with suspected esophageal perforation require contrast-enhanced swallow testing and esophagoscopy for further evaluation.

PNEUMOMEDIASTINUM

Figure 1.  Postsurgical pneumomediastinum. Close-up view from a posteroanterior chest radiograph in a 46-year-old man shows multiple streaks of air outlining the mediastinal structures (arrows). (Courtesy of Dr. Tomás Franquet, Universitat Autónoma de Barcelona, Barcelona, Spain)

Figure 3.  Pneumomediastinum with continuous diaphragm sign. Anteroposterior chest radiograph in a 58-year-old woman shows pneumomediastinum outlining the central portion of the diaphragm (arrows), a finding known as the continuous diaphragm sign. The pneumomediastinum was secondary to barotrauma related to mechanical ventilation instituted for adult respiratory distress syndrome. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Pneumomediastinum      605

Figure 2.  Pneumomediastinum after strenuous exercise. Closeup view of the chest from a posteroanterior chest radiograph in a 21-year-old man shows a long linear opacity along the left-sided heart border (arrows). (Courtesy of Dr. Tomás Franquet, Universitat Autónoma de Barcelona, Barcelona, Spain)

Figure 4.  Interstitial emphysema and pneumomediastinum in a young man with AIDS and Pneumocystis pneumonia. Closeup view from a CT scan shows gas in the anterior mediastinum and surrounding the main bronchi (black arrows). Air is also seen surrounding the intrapulmonary vessels (white arrows). Interstitial emphysema leads directly to pneumomediastinum (Macklin effect). (Courtesy of Dr. Tomás Franquet, Universitat Autónoma de Barcelona, Barcelona, Spain)

606      Pneumomediastinum

n A  lterations

in breathing pattern causing spontaneous pneumothorax: asthma, violent coughing, vomiting, athletic competition, seizure, croup, marijuana/crack smoking, pneumonia n I diopathic “spontaneous” pneumomediastinum (Hamman syndrome) in patients without history of predisposing cause and normal lung parenchyma n M  echanical ventilation with positive end-expiratory pressure (tracheostomy, endotracheal intubation) a traumatic source of pneumomediastinum in intensive care unit patients n A  ir tracking from neck into mediastinum from surgical procedures involving upper respiratory tract n D  issection of air into mediastinum after perforation of hollow viscus, ulcerative colitis, sigmoid diverticulitis, pneumatosis cystoides intestinalis, and colon procedures

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n R  upture

of alveoli most common cause of pneumomediastinum

PNEUMOMEDIASTINUM

n O  ther

conditions associated with spontaneous pneumomediastinum: seizures, croup, marijuana/crack cocaine, pneumonia, diabetic ketoacidosis, and diffuse interstitial pulmonary fibrosis n M  echanical ventilation with positive end-expiratory pressure recognized as traumatic source of pneumomediastinum in intensive care unit patients n M  ost common cause of admission of young, healthy individuals experiencing sudden chest pain or shortness of breath n P  neumomediastinum associated with mediastinitis more commonly due to communication with gastrointestinal tract or respiratory tract/head and neck soft tissue infection

Suggested Readings Bejvan SM, Godwin JD: Pneumomediastinum: Old signs and new signs. AJR Am J Roentgenol 166:1041-1048, 1996. Zylak CM, Standen JR, Barnes GR, Zylak CJ: Pneumomediastinum revisited. RadioGraphics 20:1043-1057, 2000.

Part 60 

MEDIASTINITIS

Acute Mediastinitis DEFINITION: Acute mediastinitis is focal or diffuse acute inflammation of tissues located in the middle

chest cavity.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n E  sophageal

Findings

n W  idening

and poor definition of margins of superior mediastinum n A  ir may also be seen in soft tissues of neck (subcutaneous emphysema) n P  neumomediastinum: visualization of pleura as white line adjacent to mediastinum, linear streaks of radiolucency in mediastinum, cervical soft tissues, focal retrosternal air collections, “continuous diaphragm,” V sign of Naclerio

perforation, pleural effusion, pneumomediastinum n M  ediastinal abscess n P  roper clinical setting

Utility

role of imaging in diagnosis of acute mediastinitis is confirmation of mediastinal abnormalities consistent with clinical diagnosis. n R  adiographic finding of widened mediastinum in clinical setting of fever and pleuritic chest pain strongly suggests acute mediastinitis.

is imaging modality of choice in evaluation of patients with suspected acute mediastinitis and mediastinal abscess. n N  ormal post-sternotomy findings are difficult to distinguish from mediastinitis on CT performed within first few days after surgery; CT is most helpful 2 weeks or more after surgery. n P  ercutaneous catheter aspiration and drainage of mediastinal fluid collections, under CT guidance, can be useful as diagnostic and therapeutic approach.

CT

Fluoroscopy

n S  oft

n E  xtravasation

Utility

n M  ain

Findings

tissue infiltration of mediastinal fat, obliteration of fat planes, localized fluid collections, mediastinal widening, and lymphadenopathy n G  as bubbles associated with fluid collections in up to 50% of cases n L  ow attenuation areas with rim enhancement after administration of a contrast agent suggestive of abscess formation n P  ericardial effusion, pleural effusion n E  sophageal perforation: esophageal thickening, extraluminal gas, extravasation of oral contrast material, pleural effusion n L  ate complications resulting from esophageal perforation: esophagocutaneous, esophagopleural, and esophagobronchial fistulas

n C  T

Findings

of oral contrast material into mediastinum or into pleural cavity is unequivocal sign of perforation on esophagography.

Utility

n E  sophagography

is superior to CT in demonstrating esophageal perforation.

CLINICAL PRESENTATION n C  haracteristic

clinical findings of sudden onset with chills, high fever, tachycardia, tachypnea, and prostration n R  etrosternal pain, worsened by breathing or coughing, common; radiation to the neck and ear possible

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n In

majority of patients with acute mediastinitis confident diagnosis can be made based on clinical and CT findings. n Esophagography with water-soluble contrast agent such as Gastrografin or barium is superior to CT in demonstrating esophageal perforation but is not 100% accurate. n Cross-sectional imaging techniques are generally required for diagnosis and evaluation of site and extent of mediastinal involvement. n Acute mediastinitis is potentially life-threatening condition that necessitates aggressive medical and surgical intervention.

607

608    Acute Mediastinitis

Figure 1.  Acute mediastinitis secondary to retropharyngeal abscess. A 47-year-old man presented with acute dysphagia and high fever. Clinical examination showed a retropharyngeal abscess. Close-up view from posteroanterior chest radiograph shows smooth widening of the upper mediastinum. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 3.  Acute mediastinitis secondary to esophageal perforation in a 54-year-old man. CT scan shows multiple bubbles of air in the superior mediastinum (arrows). (Courtesy of Dr. Tomàs Franquet, Universitat Autànoma de Barcelona, Barcelona, Spain)

MEDIASTINITIS

Figure 2.  Acute mediastinitis secondary to retropharyngeal abscess. A 47-year-old man presented with acute dysphagia and high fever. Clinical examination showed a retropharyngeal abscess. CT scan at the level of the aortic arch shows localized areas of low attenuation consistent with abscess formation anterior and lateral to the trachea. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 4.  Spontaneous perforation of the esophagus (Boerhaave syndrome) with mediastinal abscess in a 58-year-old man with burning substernal pain. Esophagogram shows a massive leak of barium to the mediastinum (arrows). E, esophagus. (From Giménez A, Franquet T, Erasmus JJ, et al: Thoracic complications of esophageal disorders. RadioGraphics 22:S247-S258, 2002, with permission.)

Acute Mediastinitis    609

MEDIASTINITIS

n B  oerhaave

syndrome: esophageal perforation in association with vomiting, chest pain, fever, subcutaneous emphysema, and hematemesis

DIFFERENTIAL DIAGNOSIS n A  ortic n A  cute

dissection pulmonary embolism

PATHOLOGY n F  ocal

or diffuse acute inflammation. perforation occurs secondary to diagnostic and therapeutic procedures, as well as carcinoma, irradiation, and forceful vomiting. n H  emorrhagic mediastinitis occurs with inhalational anthrax related to bioterrorism. n P  ancreatitis can extend from retroperitoneum into mediastinum and present as mediastinitis. n D  escending necrotizing mediastinitis is complication of oropharyngeal infections spreading to mediastinum through anatomic fascial planes and cervical spaces. n O  ccasionally, osteomyelitis of spine and ribs may lead to mediastinitis. n E  sophageal

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n O  ne

of the most common causes of acute mediastinitis is iatrogenic esophageal perforation during diagnostic or therapeutic endoscopic procedures. n B  oerhaave syndrome affects approximately 1 in 6000 patients. n P  ostoperative acute mediastinitis occurs in 0.5%-1.0% of patients who undergo median sternotomy for cardiothoracic surgery. n O  rganisms commonly isolated include Staphylococcus epidermidis and Staphylococcus aureus, various gramnegative organisms, fungi, and atypical mycobacteria. n R  isk of infection is increased with obesity, insulindependent diabetes, internal mammary artery grafting (especially bilaterally), and reoperation.

Suggested Readings Akman C, Kantarci F, Cetinkaya S: Imaging in mediastinitis: A systematic review based on aetiology. Clin Radiol 59:573-585, 2004. Exarhos DN, Malagari K, Tsatalou EG, et al: Acute mediastinitis: Spectrum of computed tomography findings. Eur Radiol 15:15691574, 2005. Gimenez A, Franquet T, Erasmus JJ, et al: Thoracic complications of esophageal disorders. RadioGraphics 22(Spec No):S247-S258, 2002.

Fibrosing Mediastinitis DEFINITION: Fibrosing mediastinitis is an excessive fibrotic reaction within the mediastinum usually caused by granulomatous infection. IMAGING

DIAGNOSTIC PEARLS

Radiography

n C  alcified

Findings

n G  ranulomatous

infection: localized calcified mass, usually in right paratracheal region n W  idening of mediastinum with distortion and obliteration of normally recognizable mediastinal interfaces or lines n S  uperior vena cava obstruction: prominent aortic nipple n P  arenchymal opacities n A  irway narrowing n F  indings of pulmonary venous hypertension: septal thickening and pulmonary edema n P  leural effusion Utility

n U  sually

nonspecific; frequently underestimates the extent of mediastinal disease

CT

mass, usually in paratracheal region mediastinum n C  ompression of mediastinal structures, particularly vessels and bronchi n W  idened

Utility

n S  uperior

to CT in assessment of vascular involvement not allow confident assessment of calcification, a finding highly suggestive of previous histoplasmosis or tuberculosis

n D  oes

Positron Emission Tomography Findings

n P  reliminary

reports suggest that fibrosing mediastinitis often has no uptake on FDG-PET; cases with increased uptake have also been described.

Utility

n H  elpful

Findings

n I ncreased

soft tissue with obliteration of fat planes in mediastinum or large infiltrative mass n I diopathic form usually diffuse; post-granulomatous form more commonly focal and mass-like n F  oci of calcification in localized form related to previous granulomatous infection n B  ronchial narrowing n O  bstruction or narrowing of pulmonary artery and superior vena cava. n M  ultiple collateral veins n E  nlarged left superior intercostal vein n P  arenchymal opacities: septal lines; pulmonary edema Utility

n E  xcellent

evaluation of extent of mediastinal soft tissue infiltration and calcification n I dentifies location and degree of narrowing of tracheobronchial tree n P  roperly assesses involvement of blood vessels through intravenous contrast and multiplanar reformatted imaging

in distinguishing fibrosing mediastinitis from malignancy when CT findings are nonspecific and PET shows no uptake

CLINICAL PRESENTATION n I nvolvement

of central airways: dyspnea, cough, and hemoptysis n R  ecurrent laryngeal nerve involvement: hoarseness; involvement of phrenic nerves: diaphragmatic paralysis; impingement on autonomic nerves/ganglions: Horner syndrome n E  sophageal involvement: dysphagia and chest pain; thoracic duct involvement: chylothorax and chylopericardium n S  uperior vena cava syndrome: face or neck swelling, upper extremity swelling, dyspnea, cough n P  ulmonary hypertension, cor pulmonale, refractory right-sided heart failure due to obstruction of pulmonary arteries

DIFFERENTIAL DIAGNOSIS

MRI

Findings

n T  ypically

shows heterogeneous signal intensity on T1and T2-weighted images

n L  ymphoma n P  ulmonary

n M  ediastinal

carcinoma lymphadenopathy

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n CT



n Localized



610

is imaging modality of choice in evaluating presence and extent of mediastinitis. mediastinal soft tissue mass with calcification is virtually diagnostic if correlated clinically. n In noncalcified mass or with evidence of disease progression, biopsy is required to exclude neoplasm. n Most common causes of chronic (fibrosing) mediastinitis are histoplasmosis and tuberculosis.

MEDIASTINITIS

Figure 1.  Fibrosing mediastinitis related to histoplasmosis. Close-up view of the chest from posteroanterior radiograph shows enlarged and calcified right paratracheal lymph nodes. The patient presented with superior vena cava syndrome. (Courtesy of Dr. Robert Tarver, Indiana University Medical Center, Indianapolis, IN. From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 3.  Focal fibrosing mediastinitis due to histoplasmosis in a 37-year-old woman. Axial maximal intensity projection reformatted image demonstrates that the right mediastinal mass obstructs the superior vena cava (SVC) and narrows the bronchus intermedius. (Courtesy of Dr. Renata Romano, CDPI, Rio de Janeiro, Brazil.)

Fibrosing Mediastinitis    611

Figure 2.  Focal fibrosing mediastinitis due to histoplasmosis in a 37-year-old woman. Coronal maximum intensity projection reformatted image from a multidetector CT scan shows right mediastinal mass and prominent venous collateral circulation. (Courtesy of Dr. Renata Romano, CDPI, Rio de Janeiro, Brazil.)

Figure 4.  Focal fibrosing mediastinitis due to histoplasmosis in a 37-year-old woman. CT image photographed at lung window shows right upper lobe volume loss and septal lines secondary to pulmonary venous obstruction. The patient had been treated for histoplasmosis 2 years previously. (Courtesy of Dr. Renata Romano, CDPI, Rio de Janeiro, Brazil.)

612    Fibrosing Mediastinitis

PATHOLOGY n B  enign

disorder caused by proliferation of acellular collagen and fibrous tissue within mediastinum obstructing vital structures n I diopathic form: tends to be diffuse and not associated with foci of calcification n S  econdary form: necrotizing granulomatous inflammation due to histoplasmosis or tuberculosis that tends to be focal and frequently has foci of dystrophic calcification n C  ompression of mediastinal structures n N  arrowing or occlusion of superior vena cava, pulmonary arteries and veins, and major airways

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n R  are

n G  ranulomatous

mediastinitis: most cases due to histoplasmosis (especially in North America) or tuberculosis n T  ypically affects young adults

MEDIASTINITIS

Suggested Readings Akman C, Kantarci F, Cetinkaya S: Imaging in mediastinitis: A systematic review based on aetiology. Clin Radiol 59:573-585, 2004. Atasoy C, Fitoz S, Erguvan B, Akyar S: Tuberculous fibrosing mediastinitis: CT and MRI findings. J Thorac Imaging 16:191-193, 2001. Chong S, Kim TS, Kim BT, Cho EY: Fibrosing mediastinitis mimicking malignancy at CT: Negative FDG uptake in integrated FDG PET/ CT imaging. Eur Radiol 17:1644-1646, 2007. Rossi SE, McAdams HP, Rosado-de-Christenson ML, et al: Fibrosing mediastinitis. RadioGraphics 21:737-757, 2001. Takalkar AM, Bruno GL, Makanjoula AJ, et al: A Potential role for F-18 FDG PET/CT in evaluation and management of fibrosing mediastinitis. Clin Nucl Med 32:703-706, 2007.

Part 61 

SUPERIOR VENA CAVA SYNDROME

Superior Vena Cava Syndrome DEFINITION: Superior vena cava syndrome is the name given to the clinical symptoms and signs that occur when there is partial or complete obstruction of the superior vena cava. IMAGING

DIAGNOSTIC PEARLS

Radiography

n O  bstruction

Findings n D  iffuse

mediastinal widening of the SVC frequently resulting in prominent aortic nipple from dilated left superior intercostal vein n E  nlarged and calcified right paratracheal lymph nodes in fibrosing mediastinitis related to previous histoplasmosis or tuberculosis n O  bstruction

of the SVC result from intraluminal thrombosis, neoplastic infiltration, or fibrosing mediastinitis n T  he most common cause is bronchogenic carcinoma n C  ollateral circulation systemic veins n M  ay

n L  imited

disadvantages: limited availability and lower spatial resolution than CT n R  ecommended in young patients and in follow-up of patients who require repeated examinations

CT

Angiography

n N  arrowing

n M  arked

Utility

n O  ften

first imaging modality value in the diagnosis

n M  ain

Findings

Findings

or complete obstruction of the SVC n C  ollateral circulation systemic veins n P  aratracheal lymphadenopathy, mass, or calcified nodes Utility

n C  ontrast-enhanced

CT imaging modality of choice assessment of site of obstruction and cause n C  oronal images particularly helpful in assessment of tumor extension into subcarinal region, aortopulmonary window, and SVC

stenosis or complete obstruction of SVC seen on angiography

Utility

n A  ngiography n P  erformed

useful in selected cases before stenting of SVC

n A  llows

MRI

Findings

n N  arrowing

or complete obstruction of the SVC circulation systemic veins n M  ediastinal mass n C  ollateral

CLINICAL PRESENTATION n F  ace

or neck swelling extremity swelling n D  yspnea n C  ough n D  ilated chest vein collaterals n C  hest pain n U  pper

Utility n C  an

accurately assess vascular abnormalities assessment of vascular abnormalities without ionizing radiation and without intravenous contrast

n A  llows

PATHOLOGY n O  bstruction

of SVC may result from intraluminal thrombosis, neoplastic infiltration, or fibrosing mediastinitis.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Contrast-enhanced

CT is the imaging modality of choice in the assessment of patients with SVC syndrome. n Vascular abnormalities can usually be accurately assessed with contrast-enhanced CT or MRI. n MRI allows assessment of vascular abnormalities without ionizing radiation and without use of an ­intravenous contrast agent. n Main disadvantages of MRI are limited availability and lower spatial resolution than CT. n MRI is particularly recommended in young patients and in follow-up of patients who require repeated ­examinations.

613

614    Superior Vena Cava Syndrome

Figure 1.  Focal fibrosing mediastinitis due to histoplasmosis in a 37-year-old woman. Coronal maximum intensity projection reformatted image from a multidetector CT scan shows right mediastinal mass and prominent venous collateral circulation. The patient had been treated for histoplasmosis 2 years earlier. (Courtesy of Dr. Renata Romano, CDPI, Rio de Janeiro, Brazil.)

Figure 3.  Fibrosing mediastinitis secondary to tuberculosis in a 62-year-old man presenting with SVC syndrome. Nonenhanced CT scan shows a mediastinal mass (arrow). Note small punctate calcification adjacent to the mediastinal mass. (Courtesy of Dr. Tomás Franquet, Universitant Autónoma de Barcelona, Barcelona, Spain)

SUPERIOR VENA CAVA SYNDROME

Figure 2.  Fibrosing mediastinitis secondary to tuberculosis in a 62-year-old man presenting with SVC syndrome. Angiogram confirms marked stenosis of SVC (arrows). (Courtesy of Dr. Tomás Franquet, Universitant Autónoma de Barcelona, Barcelona, Spain)

Figure 4.  Fibrosing mediastinitis secondary to tuberculosis in a 62-year-old man presenting with SVC syndrome. Contrastenhanced CT scan at same level as Figure 2 shows displacement and narrowing of the superior vena cava (arrow). Note dilation of the azygos and left superior intercostal veins (arrowheads). (Courtesy of Dr. Tomás Franquet, Universitant Autónoma de Barcelona, Barcelona, Spain)

SUPERIOR VENA CAVA SYNDROME

n O  bstruction

develops gradually; collateral veins tend to divert much of venous flow. n F  ibrosing mediastinitis is a rare benign disorder; ­proliferation of acellular collagen and fibrous tissue within mediastinum encases and obstructs vital structures.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n B  ronchogenic

carcinoma is the most common cause of SVC syndrome (80%-85%). n M  ost common benign SVC obstruction causes include fibrosing mediastinitis and iatrogenic causes (e.g., sclerosis, obstruction caused by pacemakers and central venous catheters)

Superior Vena Cava Syndrome    615

Suggested Readings Burney K, Young H, Barnard SA, et al: CT appearances of congenital and acquired abnormalities of the superior vena cava. Clin Radiol 62:837-842, 2007. Lawler LP, Corl FM, Fishman EK: Multi-detector row and volumerendered CT of the normal and accessory flow pathways of the thoracic systemic and pulmonary veins. RadioGraphics 22(Spec No):S45-S60, 2002. Rice TW, Rodriguez RM, Light RW: The superior vena cava syndrome: Clinical characteristics and evolving etiology. Medicine (Baltimore): 85:37-42, 2006. Wilson LD, Detterbeck FC, Yahalom J: Clinical practice: Superior vena cava syndrome with malignant causes. N Engl J Med 356:18621869, 2007.

Part 62 

ANTERIOR MEDIASTINUM

Normal Thymus DEFINITION: The thymus is a normal soft tissue structure in the anterior mediastinum. IMAGING

DIAGNOSTIC PEARLS

CT

n B  ilobed

Findings n B  ilobed

structure with homogeneous soft tissue atten­ uation in prevascular space, at aortic arch level, or at origin of great vessels n F  atty infiltration: lobular and speckled appearance n T  wo separate lobes (two thirds of patients) or bilobed arrowhead/triangle appearance n L  obes ovoid, elliptical, triangular, or semilunar n T  hymic lobe thickness measured perpendicular to long­ est axis of gland n L  eft lobe slightly larger than right n M  aximal normal thickness: 20 years old, 13 mm Utility

n M  ost

common imaging modality for assessment of nor­ mal and abnormal thymus in adults

MRI

Findings n S  ame

shape and location as on CT signal greater than muscle but less than fat on both T1- and T2-weighted images in patients 5.0 n M  ay be associated with Cushing syndrome or, occasionally, carcinoid syndrome

Positron Emission Tomography Findings

n H  eterogeneous

>5.0

uptake with standardized uptake value

Utility

n F  DG-PET

helpful in differential diagnosis of thymic masses n I ntegrate with CT findings to improve depiction of tumor and nodal metastases

CLINICAL PRESENTATION n C  hest

pain, cough, dyspnea, superior vena cava syndrome n O  ccasional clubbing and hypertrophic osteoarthropathy n M  ost frequent paraneoplastic syndrome: Cushing s­yndrome n C  arcinoid syndrome rare (5.0

Utility

n F  DG-PET

masses

FDG uptake with standardized uptake

helpful in differential diagnosis of thymic

n I ntegrate

with CT findings to improve depiction of tumor and nodal metastases n R  easonably accurate in differentiating thymic carcinomas from thymomas

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n U  ncommon; n T  hymic

masses

annual incidence: 1-5/million population epithelial tumors 50% of anterior mediastinal

n 1  5%-20% n O  ccurs

of all thymic epithelial tumors in middle age with male-to-female ratio of 1:1

to 2.3:1 survival rates of 20%-40%

n 5  -Year

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n CT



n MRI



624

most important imaging modality in assessment of anterior mediastinal masses helpful for evaluation of local invasion n Diagnosis confirmed by either CT-guided needle biopsy or surgical biopsy n PET/CT particularly helpful in follow-up of malignant anterior mediastinal tumors n Included in thymic carcinoma category of thymic epithelial tumors in 2004 World Health Organization classification n Aggressive tumor with poor prognosis

ANTERIOR MEDIASTINUM

Thymic Carcinoma    625

Figure 1.  Thymic squamous cell carcinoma. Contrastenhanced CT scan demonstrates anterior mediastinal mass with heterogeneous enhancement suggestive of extensive necrosis and irregular margins with the right lung (arrowheads). Surgery confirmed the presence of a thymic carcinoma. The tumor did not invade the lung. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Figure 2.  Thymic squamous cell carcinoma. T1-weighted MR image shows the fat plane between the lung and the anterior mediastinal tumor (arrowheads). Also noted is residual thymic tissue (arrow) adjacent to the tumor. Surgery confirmed the presence of a thymic carcinoma. The tumor did not invade the lung. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Figure 3.  Thymic squamous cell carcinoma. T1-weighted image in a 70-year-old man shows an anterior mediastinal mass with heterogeneous signal intensities invading the anterior chest wall (arrow), left lung (arrowheads), and ascending aorta. The tumor insinuates between the superior vena cava and the aortic arch. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Figure 4.  Thymic squamous cell carcinoma. T2-weighted image in a 70-year-old man shows an anterior mediastinal mass with heterogeneous signal intensities invading the anterior chest wall (arrow), left lung (arrowheads), and ascending aorta. The tumor insinuates between the superior vena cava and the aortic arch. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Suggested Readings Inoue A, Tomiyama N, Fujimoto K, et al: MR imaging of thymic epithelial tumors: Correlation with World Health Organization classification. Radiat Med 24:171-181, 2006. Jeong SM, Lee KY, Shin D, et al: Does CT of thymic epithelial tumors enable us to differentiate histologic subtypes and predict prognosis? AJR Am J Roentgenol 183:283-289, 2004. Jung KJ, Lee KS, Han J, et al: Malignant thymic epithelial tumors: CTpathologic correlation. AJR Am J Roentgenol 176:433-439, 2001.

Pathology and genetics of tumours of the lung, pleura, thymus, and heart. In Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors: World Health Organization Classification of Tumours. Lyon, 2004, IARC Press. Sadohara J, Fujimoto K, Müller NL, et al: Thymic epithelial tumors: Comparison of CT and MR imaging findings of low-risk thymomas, high-risk thymomas, and thymic carcinomas. Eur J Radiol 60:70-79, 2006.

Thymolipoma DEFINITION: A thymolipoma is a mesenchymal tumor in the mediastinum consisting of adipose and

thymic tissue.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n L  ow-density

Findings n L  arge

anterior mediastinal mass that may extend to inferior hemithorax on one or both sides of midline. n M  imics cardiomegaly or elevated hemidiaphragm. n L  ow density of mass may be appreciated n M  ay change shape or position on decubitus view Utility

n M  ajority

found incidentally on chest radiography

mediastinal mass that changes with position n A  reas of fat and soft tissue attenuation on CT n M  ay be associated with myasthenia gravis

DIFFERENTIAL DIAGNOSIS

CT

n T  eratoma

n A  nterior

n T  hymic

Findings

mediastinal mass with smooth margins n P  redominant fat attenuation or equivalent fat and soft tissue attenuation

n T  hymoma

carcinoma lipomatosis

n M  ediastinal

Utility

n U  seful

in detecting connection to thymus dependent on relative amounts of adipose tissue and thymus n A  ccurate diagnosis achieved in most cases owing to characteristic findings n A  ttenuation

MRI

PATHOLOGY n B  enign

mesenchymal tumor consisting of mature a­ dipose tissue with areas of non-neoplastic thymic ­tissue n R  ange from 4-30 cm in diameter; most weigh >500 g

Findings

n A  nterior

mediastinal mass with smooth margins signal intensity on T1-weighted imaging (fat) with areas of intermediate signal (soft tissue) n L  oss of fat signal on fat-suppressed imaging n H  igh

Utility

n U  seful

in detecting connection to thymus intensity dependent on relative amounts of adipose tissue and thymus n F  at suppression or chemical shift imaging helpful in assessing fat content n A  ccurate diagnosis achieved in most cases owing to characteristic findings n S  ignal

CLINICAL PRESENTATION n M  ostly

asymptomatic, found incidentally on radiography with myasthenia gravis (7%)

n A  ssociation

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n U  ncommon,

40 years of age. syndromes associated with thymoma include myasthenia gravis (40%), pure red cell aplasia, hypogammaglobulinemia, and stiff person syndrome. n Eighty percent of patients with thymoma and myasthenia gravis have positive serum anti-acetylcholine receptor binding antibody with specificity of 98%. n CT is most important imaging modality in assessment of anterior mediastinal masses; MRI is helpful for evaluation of local invasion. n Diagnosis can be confirmed by either CT-guided needle biopsy or surgical biopsy. n World Health Organization Classification includes thymomas and thymic carcinomas together under thymic epithelial tumors.

ANTERIOR MEDIASTINUM

Figure 1.  Type AB thymoma in a 70-year-old woman. Contrastenhanced CT demonstrates a smoothly marginated mass with relatively homogeneous enhancement and linear areas of low attenuation. Thymic vein (small arrow) and dilated feeders (large arrow) are seen in the adjacent mediastinum. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Figure 3.  Type B2 thymoma in a 56-year-old woman. T1weighted image demonstrates a lobulated-contour mass adhering tightly to the right lung (Masaoka stage III). Low signal intensity lines subdivide the mass into lobules. Histologically the tumor was shown to be a type B2 thymoma. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Thymoma      629

Figure 2.  Type B3 thymoma. Contrast-enhanced CT image demonstrates a heterogeneous enhancing mass with partially spiculated margins and with ring-like (black arrow) and punctate calcifications. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

Figure 4.  Type B2 thymoma in a 56-year-old woman. T2weighted image demonstrates a lobulated-contour mass adhering tightly to the right lung (Masaoka stage III). Low signal intensity lines subdivide the mass into lobules. Histologically the tumor was shown to be a type B2 thymoma. (Courtesy of Dr. Kiminori Fujimoto, Kurume, Fukuoka, Japan)

630      Thymoma

Positron Emission Tomography Findings

n H  eterogeneous

value 2 minutes) after intravenous injection of a contrast agent n I ntense prolonged contrast enhancement n F  ocal nonenhancing areas of low attenuation secondary to hemorrhage or cyst formation n M  ost common cause: goiter, typically with sharply defined smooth margins n C  arcinoma: may have homogeneous or inhomogeneous attenuation and well-defined or poorly defined margins n C  ervical or mediastinal lymphadenopathy Utility

n S  uperior

to radiography for diagnosis and assessment of extent n T  hyroid carcinoma likely if evidence of spread into adjacent tissue or lymphadenopathy

Ultrasonography

uptake of iodine on 131I scintigraphy

n H  elpful

in the staging of thyroid cancer and in the assessment of tumor recurrence

Positron Emission Tomography Findings

n I ncreased

uptake of FDG on PET in patients with thyroid cancer

Utility

n P  ET-CT

helpful in staging of thyroid carcinoma and assessment of tumor recurrence n H  elpful mainly in patients with negative 131I scintigraphy

CLINICAL PRESENTATION n I ntrathoracic

goiter usually asymptomatic have respiratory distress (worsened by certain neck movements) n H  oarseness n M  ay

DIFFERENTIAL DIAGNOSIS n T  hymoma n G  erm

Findings

n E  nlarged

thyroid gland or focal mass or decreased echogenicity compared with the normal gland n C  ervical lymphadenopathy n I ncreased

Utility

n I mportant

in workup of thyroid nodules and masses modality of choice to guide needle biopsy of thyroid lesions

n I maging

cell tumor: Teratoma carcinoma n L  ymphoma n T  hymic

PATHOLOGY n M  ultinodular

goiter, thyroiditis, or thyroid carcinoma from lower pole or isthmus and extend into anterior or middle mediastinum (80%)

n A  rise

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n CT



n Ultrasonography

648

is most important imaging modality in assessment of mediastinal masses. is the imaging modality of choice to guide needle biopsy of thyroid lesions

Thyroid Masses    649

ANTERIOR MEDIASTINUM

Figure 1.  Multinodular goiter. CT scan performed during intravenous administration of contrast material shows a large anterior mediastinal mass that has inhomogeneous attenuation and contains small foci of calcification. The mass lies anterior to the aortic arch (AA) and innominate artery and displaces the left brachiocephalic vein (arrow). The patient was a 67-year-old woman with long-standing multinodular goiter. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

n R  emainder

arise from posterior aspect of either thyroid lobe and extend into posterior aspect of mediastinum behind the trachea

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ost

common mediastinal thyroid mass is multinodular goiter. n D  iagnosis noted most commonly in women in their 40s. n A  pproximately 80% of mediastinal thyroid tumors arise from lower pole or isthmus and extend into anterior or middle mediastinum.

Suggested Readings Hegedüs L: Clinical practice: The thyroid nodule. N Engl J Med 351:1764-1771, 2004. Hoang JK, Lee WK, Lee M, et al: US Features of thyroid malignancy: Pearls and pitfalls. RadioGraphics 27:847-860, 2007; discussion 861–865. Imhof H, Czerny C, Hörmann M, Krestan C: Tumors and tumor-like lesions of the neck: From childhood to adult. Eur Radiol 14(Suppl 4):L155-L165, 2004. Wang TS, Cheng DW, Udelsman R: Contemporary imaging for thyroid cancer. Surg Oncol Clin North Am 16:431-445, 2007. Weber AL, Randolph G, Aksoy FG: The thyroid and parathyroid glands: CT and MR imaging and correlation with pathology and clinical findings. Radiol Clin North Am 38:1105-1129, 2000.

Part 63 

 IDDLE AND POSTERIOR M MEDIASTINAL MASSES

Unilateral Hilar Lymphadenopathy DEFINITION: Unilateral lymph node enlargement exists when these nodes have a short-axis diameter >10 mm. IMAGING

DIAGNOSTIC PEARLS

Radiography

n I ncreased

Findings

n U  nilateral

hilar lymphadenopathy size and opacity of the hilum and a lobulated contour

n I ncreased

Utility

n F  irst

and often only imaging modality used

CT

n U  nilateral

hilar lymphadenopathy is evident. n E  nlarged nodes may have homogeneous or inhomogeneous appearance and be hypoattenuating or show diffuse or rim enhancement after intravenous administration of a contrast agent. n R  im enhancement and a low-attenuation center are seen most commonly in patients with tuberculosis. n T  he hilar lymph nodes include the peribronchial and bronchopulmonary lymph nodes (stations 10 and 11 in the American Thoracic Society classification) Utility

n S  uperior

to radiography in demonstrating presence of lymphadenopathy and associated findings n H  ilar nodes best seen after intravenous administration of a contrast agent

MRI

n U  nilateral

Utility

Positron Emission Tomography Findings

Findings

Findings

size and opacity of the hilum contour of the hilum n S  hort-axis diameter greater than 10 mm on CT n C  ommon causes: pulmonary carcinoma, tuberculosis, bacterial pneumonia, lymphoma n L  obulated

n I ncreased

Utility

FDG uptake

n S  uperior

to CT and MRI in distinguishing benign from malignant lymphadenopathy n Limited specificity

CLINICAL PRESENTATION n T  he

condition is asymptomatic, or symptoms related to an underlying cause are noted. n W  eight loss, cough, and hemoptysis are suggestive of pulmonary carcinoma. n F  ever and night sweats are suggestive of infection (tuberculosis, histoplasmosis, coccidioidomycosis).

PATHOLOGY hilar lymphadenopathy

n S  imilar

to CT in demonstrating presence of enlarged hilar nodes n A  dvantage over CT: lack of radiation or need for a contrast agent

n M  ediastinal

and hilar lymph nodes are considered enlarged when their short-axis diameter is >10 mm. n N  eoplastic causes include pulmonary carcinoma, ­lymphoma, metastasis from kidney, breast, head and neck tumor. n I nfectious causes include tuberculosis, histoplasmosis, coccidioidomycosis, and bacterial pneumonia.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

650

n Once

mediastinal or hilar abnormality is detected or suspected on the chest radiograph, cross-sectional imaging is performed. n Contrast-enhanced CT is the imaging modality of choice in the assessment of hilar lymphadenopathy and associated findings in adults. n Unilateral hilar lymphadenopathy is most commonly due to neoplasm (pulmonary carcinoma, lymphoma, or metastasis from kidney, breast, or head and neck tumor). n Association is also common with infection (e.g., tuberculosis, histoplasmosis, coccidioidomycosis, bacterial pneumonia, lung abscess).

MIDDLE AND POSTERIOR MEDIASTINAL MASSES

Figure 1.  Chest radiograph shows increased size and lobulated contour of the left hilum. The patients was a 33-year-old man with primary tuberculosis.

Unilateral Hilar Lymphadenopathy    651

Figure 2.  Contrast-enhanced CT demonstrates enlarged right hilar lymph nodes. The patient was a 64-year-old man with pulmonary carcinoma.

Figure 3.  Unilateral hilar lymphadenopathy in a patient with AIDS and tuberculosis. Contrast-enhanced CT image shows hypodense right hilar lymphadenopathy. (Courtesy of Dr. Joel E. Fishman University of Miami, Miami, Florida)

n I nfectious

granulomas: lymphadenopathy tends to be unilateral. n T  uberculosis: lymph node enlargement is on side of lung disease, but involvement of contralateral nodes is not rare.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n U  nilateral

hilar lymphadenopathy is most commonly due to neoplasm (pulmonary carcinoma, lymphoma, or metastasis from kidney, breast, or head and neck tumor). n A  ssociation is also common with infection (e.g., tuberculosis, histoplasmosis, coccidioidomycosis, bacterial pneumonia, lung abscess).

n U  nilateral

hilar lymphadenopathy is particularly common in primary tuberculosis and tuberculosis associated with AIDS.

Suggested Readings Boiselle PM, Patz EF Jr, Vining DJ, et al: Imaging of mediastinal lymph nodes: CT, MR, and FDG PET. RadioGraphics 18:10611069, 1998. Müller NL, Webb WR: Radiographic imaging of the pulmonary hila. Invest Radiol 20:661-671, 1985. Sharma A, Fidias P, Hayman LA, et al: Patterns of lymphadenopathy in thoracic malignancies. RadioGraphics 24:419-434, 2004.

Bilateral Hilar Lymphadenopathy DEFINITION: Bilateral hilar lymphadenopathy exists when these lymph nodes have a short-axis ­diameter >10 mm.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  arcoidosis:

Findings

n B  ilateral

symmetric or asymmetric hilar lymph node enlargement is evident. n E  nlarged nodes result in lobulation and increased size and opacity of the hila. n S  ymmetric hilar lymphadenopathy in a patient without systemic symptoms is most suggestive of sarcoidosis. n A  symmetric hilar lymphadenopathy or presence of systemic symptoms (fever, night sweats) should raise the suspicion of lymphoma or another neoplasm. n S  tage I sarcoidosis is symmetric bilateral hilar and mediastinal lymph node enlargement without parenchymal abnormality. n S  tage II sarcoidosis is symmetric bilateral hilar and mediastinal lymph node enlargement plus parenchymal abnormality. Utility

n U  sually

first imaging modality used

CT

symmetric bilateral hilar and mediastinal lymphadenopathy in young adults with no systemic symptoms n C  ommon causes of bilateral symmetric hilar lymphadenopathy: sarcoidosis, lymphoma, metastases (renal cell carcinoma, testicular tumor), and silicosis n C  ommon causes of bilateral asymmetric hilar lymphadenophathy: lymphoma, sarcoidosis, and metastases (renal cell carcinoma, testicular tumor, breast cancer, pulmonary carcinoma)

MRI

Findings

n B  ilateral

Utility

n C  omparable

to CT in the assessment of hilar and mediastinal lymphadenopathy

Positron Emission Tomography Findings

Findings

n B  ilateral

symmetric or asymmetric hilar lymph node enlargement n M  ediastinal lymph node enlargement commonly present n S  hort-axis diameter >10 mm n T  he hilar lymph nodes include the peribronchial and bronchopulmonary lymph nodes (stations 10 and 11 in the American Thoracic Society classification) Utility n C  T

is superior to radiography in demonstrating presence of hilar lymphadenopathy and associated findings. n S  lightly enlarged nodes are best seen after intravenous contrast agent administration.

hilar lymph node enlargement

n I ncreased

Utility

FDG uptake

n S  uperior

to CT and MRI in distinguishing benign from malignant lymphadenopathy

CLINICAL PRESENTATION n T  hirty

percent to 50% of patients with sarcoidosis are asymptomatic, with sarcoidosis being first suspected based on the presence of bilateral hilar lymphadenopathy on routine chest radiographs. n C  ommon symptoms in sarcoidosis include dyspnea, cough, and chest pain. n P  atients with lymphoma usually present with systemic symptoms, including fever, night sweats, and weight loss.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

652

n Symmetric

hilar lymphadenopathy in patient without systemic symptoms is most suggestive of sarcoidosis. n Asymmetric hilar lymphadenopathy or presence of systemic symptoms (fever, night sweats) should raise suspicion of lymphoma or another neoplasm or infection. n CT and MRI are comparable in the assessment of hilar and mediastinal lymphadenopathy. n In clinical practice, contrast-enhanced CT is usually performed to further evaluate presence and extent of lymphadenopathy. n PET, particularly when combined with CT (PET-CT), is superior to CT and MRI in the staging of carcinoma and lymphoma.

MIDDLE AND POSTERIOR MEDIASTINAL MASSES

Figure 1.  Stage I sarcoidosis. Posteroanterior chest radiograph in a 33-year-old man with sarcoidosis shows right paratracheal, aortopulmonary window, and symmetric bilateral hilar lymph node enlargement.

Bilateral Hilar Lymphadenopathy    653

Figure 2.  Stage II sarcoidosis. Posteroanterior chest radiograph in a 35-year-old man with sarcoidosis demonstrates right paratracheal, aortopulmonary window, and symmetric bilateral hilar lymph node enlargement and small round and irregular opacities in the upper zones. Note medial deviation of the gastric bubble due to splenomegaly.

Figure 3.  Mixed cellularity Hodgkin disease in a 20-year-old woman. CT scan obtained at level of basal trunk demonstrates extensive bilateral hilar nodal enlargement. Also note multiple pulmonary nodules (arrows) and right middle lobe consolidation. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 4.  Nodular sclerosing Hodgkin disease in a 25-yearold woman. PET scan demonstrates increased FDG uptake in mediastinal and hilar nodes bilaterally. Also note FDG uptake in bilateral supraclavicular and left lower neck nodes (arrows), which were not identified on conventional staging methods. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

654    Bilateral Hilar Lymphadenopathy

PATHOLOGY n M  ost

common cause of bilateral symmetric hilar lymphadenopathy is sarcoidosis. n O  ther causes include Hodgkin and non-Hodgkin lymphoma, metastases (renal cell carcinoma, testicular tumor, breast cancer), cystic fibrosis, and silicosis. n C  ommon causes of bilateral asymmetric lymphadenopathy include Hodgkin and non-Hodgkin lymphoma, sarcoidosis, and metastases (pulmonary carcinoma, renal cell carcinoma, testicular tumor, breast cancer). n L  ess common causes of bilateral hilar lymphadenopathy include leukemia, multicentric giant lymph node hyperplasia (Castleman disease), granulomatous infection (tuberculosis, histoplasmosis), and Löfgren syndrome (triad of bilateral hilar lymphadenopathy, erythema nodosum, polyarticular arthralgia).

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ost

common cause of bilateral symmetric hilar lymphadenopathy is sarcoidosis.

MIDDLE AND POSTERIOR MEDIASTINAL MASSES

n C  ommon

causes of bilateral asymmetric lymphadenopathy include Hodgkin and non-Hodgkin lymphoma, leukemia, sarcoidosis, and metastases (pulmonary carcinoma, renal cell carcinoma, testicular tumor, breast cancer). n L  ess common causes of bilateral hilar lymphadenopathy include leukemia, multicentric giant lymph node hyperplasia (Castleman disease), and granulomatous infection (tuberculosis, histoplasmosis)

Suggested Readings Boiselle PM, Patz EF Jr, Vining DJ, et al: Imaging of mediastinal lymph nodes: CT, MR, and FDG PET. RadioGraphics 18:1061-1069, 1998. Müller NL, Webb WR: Radiographic imaging of the pulmonary hila. Invest Radiol 20:661-671, 1985. Nunes H, Brillet PY, Valeyre D, et al: Imaging in sarcoidosis. Semin Respir Crit Care Med 28:102-120, 2007. Sharma A, Fidias P, Hayman LA, et al: Patterns of lymphadenopathy in thoracic malignancies. RadioGraphics 24:419-434, 2004.

Mediastinal Lymphadenopathy DEFINITION: Mediastinal lymphadenopathy exists when mediastinal lymph nodes have a short-axis diameter >10 mm.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n E  nlarged

Findings

n W  idening

of paratracheal stripe opacity and a convexity in the region of superior vena cava n I ncreased opacity and a convexity in the region of aortopulmonary window n I ncreased opacity and a convexity in the subcarinal region n M  ediastinal widening n I ncreased

mediastinal lymph nodes symmetric bilateral hilar and mediastinal lymphadenopathy in young adults with no systemic symptoms n L  ymphoma or metastasis: asymmetric lymphadenopathy with systemic symptoms n S  evere infection, fibrosing mediastinitis, aggressive neoplasm: poor definition of lymph node margins and obscuration of adjacent fat n S  arcoidosis:

Utility

n R  adiography

is often the initial imaging modality performed in patients with suspected hilar or mediastinal lymphadenopathy, although it is of limited accuracy in the diagnosis of mediastinal lymphadenopathy. n S  ymmetric bilateral hilar and mediastinal lymphadenopathy in young adults with no systemic symptoms is suggestive of sarcoidosis. n A  symmetric bilateral hilar and mediastinal lymphadenopathy in patients with systemic symptoms is suggestive of lymphoma or metastases.

n S  ymmetric

bilateral hilar and mediastinal lymphadenopathy in young adults with no systemic symptoms is suggestive of sarcoidosis. n A  symmetric bilateral hilar and mediastinal lymphadenopathy in patients with systemic symptoms is suggestive of lymphoma or metastases.

MRI

Findings

n E  nlarged

Utility

CT

mediastinal lymph nodes

n U  sed

Findings

n E  nlarged mediastinal nodes: short-axis diameter >10 mm n S  arcoidosis:

symmetric bilateral hilar and mediastinal lymphadenopathy n L  ymphoma or metastasis: asymmetric lymphadenopathy n S  evere infection, fibrosing mediastinitis, aggressive neoplasm: poor definition of lymph node margins and obscuration of adjacent fat n G  ranulomatous infections: foci of necrosis or calcification n T  uberculosis, fungal infection, metastasis from bronchogenic carcinoma, lymphoma: low attenuation after intravenous administration of a contrast agent n G  iant lymph node hyperplasia (Castleman disease): marked enhancement of single enlarged mediastinal lymph node group

to assess the location and extent of the findings to CT in the assessment of mediastinal lymphadenopathy

n C  omparable

Positron Emission Tomography Findings

n I ncreased

Utility

uptake on FDG-PET

n F  DG-PET

relies on increased metabolic rate of neoplastic cells and is superior to CT and MRI in distinguishing malignant from benign nodes. n I ncreased uptake (false-positive diagnosis) may also occur with active inflammation or infection. n F  alse-negative diagnosis occurs mainly in small nodes. n I ntegrated PET/CT is superior to CT or PET.

Utility

n O  nce

mediastinal or hilar abnormality is detected/­ suspected on chest radiograph, cross-sectional imaging is usually performed. n C  T is used to assess the location and extent of the ­findings.

CLINICAL PRESENTATION n A  symptomatic

or nonspecific symptoms of fever, malaise, and weight loss

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n CT



n Mediastinal



is the imaging modality of choice to assess the presence and extent of mediastinal lymphadenopathy. lymph nodes are considered enlarged when their short-axis diameter is > 10 mm on CT. n CT and MRI assess mainly lymph node size; they are of limited value in distinguishing malignant from benign lymph node enlargement. n Integrated PET/CT is superior to CT or MRI in distinguishing benign from malignant lymph nodes. n PET/CT is of limited value in distinguishing enlarged lymph nodes due to active infection from malignancy.

655

656    Mediastinal Lymphadenopathy

Figure 1.  Middle and posterior mediastinal lymphadenopathy. Contrast-enhanced CT image shows enlarged lymph nodes in the paratracheal, prevascular, and subcarinal spaces. Hilar nodes are also evident. The patient was a 67-year-old woman with chronic lymphocytic leukemia.

MIDDLE AND POSTERIOR MEDIASTINAL MASSES

Figure 2.  Middle and posterior mediastinal lymphadenopathy. Same patient as in Figure 1. Contrast-enhanced CT image shows enlarged lymph nodes in the paratracheal, prevascular, and subcarinal spaces. Hilar nodes are also evident. The patient was a 67-year-old woman with chronic lymphocytic leukemia.

Figure 3.  True positive integrated PET/CT in a 70-year-old man with adenocarcinoma of lung. Contrast-enhanced CT scan shows enlarged lymph nodes in para-aortic (station 6, arrow) and subaortic (station 5, arrowhead) areas. Also note obstructive atelectasis in left upper lobe. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 4.  True positive integrated PET/CT in a 70-year-old man with adenocarcinoma of lung. Same patient as in Figure 3. PET and integrated PET/CT show increased FDG uptake (maximum standardized uptake value, 11.5) in enlarged nodes (arrows) as well as primary lung cancer. The patient had surgically confirmed lymph node metastases. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Mediastinal Lymphadenopathy    657

MIDDLE AND POSTERIOR MEDIASTINAL MASSES

PATHOLOGY n M  ediastinal

lymph nodes are considered enlarged when their short-axis diameter is >10 mm. n C  ommon causes of enlarged mediastinal lymph nodes include lymphoma, metastases, granulomatous infections, and sarcoidosis. n M  ediastinal lymph nodes can also be involved in patients with leukemia, particularly lymphocytic ­leukemia. n P  rimary malignancies that commonly metastasize to intrathoracic lymph nodes include tumors of head and neck, genitourinary tract, and breast and malignant melanoma. n M  etastases are frequently accompanied by lymphangitic or hematogenous spread to the lungs. n I nvolvement of the anterior and posterior mediastinal lymph nodes is unusual in the absence of middle mediastinal lymphadenopathy. n L  ymph nodes may be separated by fat or may conglomerate into multiple large masses.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n E  nlarged

lymph nodes are one of the most frequent causes of mediastinal masses.

n U  p

to 85% of patients with Hodgkin lymphoma pre­ sent with mediastinal lymph node enlargement (prevascular, paratracheal, hilar, subcarinal node groups). n E  xtension of the nodal disease to the lungs occurs in approximately 10% of patients. n I nvolvement of a single lymph node group, usually the prevascular and/or pretracheal, is much more common in patients with non-Hodgkin lymphoma. n M  ediastinal lymph nodes are involved in 60%-90% of patients with sarcoidosis.

Suggested Readings Boiselle PM, Patz EF Jr, Vining DJ, et al: Imaging of mediastinal lymph nodes: CT, MR, and FDG PET. RadioGraphics 18:10611069, 1998. de Langen AJ, Raijmakers P, Riphagen I, et al: The size of mediastinal lymph nodes and its relation with metastatic involvement: A metaanalysis. Eur J Cardiothorac Surg 29:26-29, 2006. Dooms C, Vansteenkiste J: Positron emission tomography in non– small cell lung cancer. Curr Opin Pulm Med 13:256-260, 2007. Schrevens L, Lorent N, Dooms C, Vansteenkiste J: The role of PET scan in diagnosis, staging, and management of non-small cell lung cancer. Oncologist 9:633-643, 2004. Sharma A, Fidias P, Hayman LA, et al: Patterns of lymphadenopathy in thoracic malignancies. RadioGraphics 24:419-434, 2004.

Azygos and Hemiazygos Veins: Normal and Abnormal Findings DEFINITION: The azygos and hemiazygos veins may become dilated in heart failure, obstruction of the superior vena cava, interruption of the inferior vena cava, and portal hypertension.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n R  ound

Findings n A  zygos

vein is normally seen as an elliptical opacity in the region of the right tracheobronchial angle. n T  ransverse diameter of azygos vein at right tracheobronchial angle level is normally 5 cm in diameter, low-attenuation areas within primary tumor, irregular/ill-defined margins, adjacent structure compression/destruction n P  leural abnormalities (e.g., pleural effusion or pleural nodules, presence of metastatic pulmonary nodules) Utility

n O  ften

allows diagnosis of nerve sheath tumor

MRI

and neurofibroma: well-demarcated round or elliptical masses with smooth margins; may have “dumbbell” or “hourglass” configuration n M  alignant nerve sheath tumor: lesions >5 cm in diameter, irregular/ill-defined margins, adjacent structure compression/destruction n V  ery

high signal intensity areas on T2-weighted images corresponding pathologically to areas of cystic degeneration n G  adolinium-enhanced MR images with contrast enhancement in peripheral portion of tumor and no enhancement in areas of cystic degeneration n N  eurofibromas: homogeneous low-intermediate signal intensity on T1-weighted MR images; target appearance on T2-weighted sequence Utility

n S  hould

be performed preoperatively in all patients with suspicious neurogenic tumors to definitely exclude intraspinal tumor extension

CLINICAL PRESENTATION n O  ften n P  ain

asymptomatic and neurologic symptoms

DIFFERENTIAL DIAGNOSIS n M  esenchymal

tumor tumor of the pleura n D  uplication cysts n M  eningocele n P  ulmonary carcinoma n F  ibrous

Findings

n N  eurilemomas:

low-intermediate signal intensity on T1-weighted images; areas of intermediate-high signal intensity on T2-weighted sequences

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Prognosis



n Recurrences



680

of neurilemoma is excellent, and recurrence is rarely reported after surgical resection. in neurofibromas are rare after surgical resection. n Recurrences in malignant nerve sheath tumor are common even after surgical resection. n Majority of paravertebral masses in adults are benign.

PARAVERTEBRAL MASSES

Figure 1.  Schwannoma in a 31-year-old woman. Chest radiograph shows large well-defined soft tissue mass in right upper and middle lung zones with its broad base in the mediastinum. Also note widening of intercostal spaces (arrows), especially between right fifth and sixth ribs. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 3.  Neurofibromas in a 20-year-old man with neurofibromatosis. Unenhanced T1-weighted MR image obtained at level of great vessels shows soft tissue masses with globular enhancing portion in bilateral paraspinal areas and left axilla and along the course of left intercostal (arrowheads) and bilateral vagus (curved arrows) nerves. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Nerve Sheath Tumors    681

Figure 2.  Cellular schwannoma in a 70-year-old woman. Contrast-enhanced CT image obtained at level of liver dome shows dumbbell-shaped soft tissue mass along course of intercostal nerve. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 4.  Neurofibromas in a 20-year-old man with neurofibromatosis. In the same patient as Figure 3, T2-weighted MR image shows slightly heterogeneous, but mainly high signal intensity lesions at same sites on previous image (see Fig. 3). Also note small neurofibromas (arrows) in the posterior chest wall. Some lesions in left paraspinal region and left chest wall show target sign (peripheral high and central low signal intensity). (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

682    Nerve Sheath Tumors

PATHOLOGY n N  eurilemomas

grow by formation of lateral mass on parent nerve, compressing it; they are encapsulated with nerve fibers stretched around the tumor. n H  istologically, they consist of two components: highly ordered cellular component (Antoni type A) and loose myxoid component (Antoni type B). n T  hey occur in the paravertebral region, along vagus/ phrenic nerve, along a rib, in the anterior mediastinum, and in the brachial plexus. n N  eurofibromas are tumors of cranial, spinal, or peripheral nerves, which are intimately continuous with the nerve proper. n A  ffected nerve is circumferentially compressed or diffusely penetrated by elements of tumor. n P  roliferation of nerve sheath cells interspersed with thick wavy collagen bundles occurs, and there may be variable degrees of myxoid degeneration.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n O  ver

90% of peripheral nerve tumors are benign; benign lesions are identified in young and middle-aged adults.

PARAVERTEBRAL MASSES

n N  eurilemoma

has equal frequency in men and women and affects all ages (mean age, 41 years). n N  eurofibroma is more frequent in men, usually second to fourth decades of age at diagnosis n M  alignant nerve sheath tumors account for up to 15% of nerve sheath tumors. n I ncidence of sarcomatous degeneration in patients with neurofibromatosis is approximately 5%. n M  alignant nerve sheath tumors have equal involvement in men and women; they are common in persons 20-50 years of age.

Suggested Readings Ko SF, Lee TY, Lin JW, et al: Thoracic neurilemomas: An analysis of computed tomography findings in 36 patients. J Thorac Imaging 13:21-26, 1998. Lee JY, Lee KS, Han J, et al: Spectrum of neurogenic tumors in the thorax: CT and pathologic findings. J Comput Assist Tomogr 23:399-406, 1999. Tanaka O, Kiryu T, Hirose Y, et al: Neurogenic tumors of the mediastinum and chest wall: MR imaging appearance. J Thorac Imaging 20:316-320, 2005.

Sympathetic Ganglia Tumors (Ganglioneuromas, Ganglioneuroblastomas, and Neuroblastomas) DEFINITION: Tumors of the sympathetic ganglia include ganglioneuromas, ganglioneuroblastomas, and neuroblastomas.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n G  anglioneuroma/ganglioneuroblastoma:

Findings

n G  anglioneuromas

and ganglioneuroblastomas are elongated and oriented in a vertical axis following direction of sympathetic chain n G  anglioneuroma: well-defined, oval lesion with little mass effect relative to size of tumor n G  anglioneuroblastoma: well-defined, oval lesion usually oriented in vertical axis following sympathetic chain direction n N  euroblastoma: paravertebral in location; contains calcification (10%); results in rib and vertebral erosion Utility

n U  sually

initial modality in the assessment of patients with suspected mediastinal or paravertebral abnormality

CT

Findings

n G  anglioneuroma:

low attenuatison (unenhanced CT); mild/moderate enhancement after intravenous administration of a contrast agent n C  alcification pattern: discrete and punctate (ganglioneuroma); amorphous and coarse (neuroblastoma) n G  anglioneuroblastoma: variable, ranging from homogeneous solid mass to predominantly cystic mass with few thin strands of soft tissue attenuation n N  euroblastoma: lobulated contour, lacks a capsule, inhomogeneous attenuation due to tumor necrosis Utility

n S  uperior

to chest radiography in demonstrating presence and extent of paravertebral masses n F  oci of calcification seen in approximately 20% of patients

MRI

elongated oval tumors typically oriented along the sympathetic chain n G  anglioneuroblastoma: ranging from homogeneous solid mass to predominantly cystic mass with a few thin strands of soft tissue n N  euroblastoma: inhomogeneous attenuation due to tumor necrosis n N  euroblastomas and ganglioneuroblastomas occur in infants and young children n G  anglioneuromas occur in older children and young adults n W  horled

appearance caused by curvilinear/nodular bands of low signal intensity on T1-weighted images; heterogeneous high signal intensity on T2-weighted images n V  ariable enhancement with gadolinium n N  euroblastoma: homogeneous or heterogeneous signal intensity on all sequences and variable enhancement after gadolinium administration Utility n B  est

imaging modality for assessment of tumor extension into spinal canal

CLINICAL PRESENTATION n S  igns

and symptoms include fatigue, loss of appetite, weight loss, and chest discomfort. n L  arge tumors may result in dyspnea.

PATHOLOGY n G  anglioneuromas

Findings

n G  anglioneuroma:

homogeneous lesion of intermediate signal intensity on both T1- and T2-weighted sequences

are encapsulated benign tumors, attached to either sympathetic or intercostal nerve trunk; they arise anywhere along paravertebral sympathetic plexus and adrenal medulla and are composed of large ganglion cells, nerve sheath cells, and nerve fibers.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Ganglioneuromas:



n Ganglioneuroblastoma:



prognosis is excellent and recurrences are rare after surgical resection. response to therapy and prognosis are significantly more favorable than those of neuroblastomas. n Neuroblastomas: there is a wide spectrum of clinical behavior ranging from spontaneous regression to aggressive disease with metastatic dissemination leading to death.

683

684    Sympathetic Ganglia Tumors

PARAVERTEBRAL MASSES

Figure 1.  Ganglioneuroma in a 14-year-old girl. Chest radiograph shows vertically oriented, well-defined soft tissue mass in the medial aspect of the left upper lung zone with its broad base in the mediastinal side. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 2.  Ganglioneuroma in a 14-year-old girl. In the same patient as Figure 1, close-up view from contrast-enhanced CT scan obtained at level of distal main bronchi shows pear-shaped, homogeneous, low-attenuation, soft tissue mass in left paraspinal area. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 3.  Neuroblastoma in a 6-year-old boy. Contrastenhanced CT scan obtained at level of great vessels shows inhomogeneously enhancing soft tissue mass occupying left paraspinal area. Mass extends into spinal canal (arrows). Also note calcifications (arrowheads) within mass lesion. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

Figure 4.  Neuroblastoma in a 6-year-old boy. In the same patient as Figure 3, gadolinium-enhanced T1-weighted MR image shows heterogeneously enhancing mass. Also note intraspinal component (arrows) of tumor. (Courtesy of Dr. Kyung Soo Lee, Seoul, Korea)

PARAVERTEBRAL MASSES

Sympathetic Ganglia Tumors    685

n G  anglioneuroblastomas

are transitional tumors containing elements of both malignant neuroblastoma and benign ganglioneuroma; they may be partially or totally encapsulated and frequently contain granular calcification. n N  euroblastomas are of neural crest origin and usually arise in adrenal glands; they are composed of small, dark neuroepithelial cells showing glial/ganglionic differentiation and contain primitive round cells with dark-staining nuclei and scanty cytoplasm and may show gross or microscopic calcification but lack any capsular structures.

n G  anglioneuromas

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

Suggested Readings

n T  hese

tumors occur predominantly in infants and c­ hildren. n M  alignant tumors are noted in younger patients, and benign lesions are observed in older children or ­adolescents. n N  euroblastoma accounts for approximately 10% of pediatric cancers and 15% of cancer deaths in ­children.

occur in all age groups, but 60% are seen in patients < age 20 years; males are more ­frequently affected. n G  anglioneuroblastomas are seen in young children but are rare after age of 10; there is an equal frequency in boys and girls. n N  euroblastomas are childhood neoplasms; boys are affected more than girls, and 90% are diagnosed in the first 8 years of life. n O  verall 2-year survival for mediastinal primary neuroblastoma is >60%. n P  rimary intrathoracic neuroblastomas comprise 14% of all neuroblastomas.

Ichikawa T, Ohtomo K, Araki T, et al: Ganglioneuroma: Computed tomography and magnetic resonance features. Br J Radiol 69:114121, 1996. Lonergan GJ, Schwab CM, Suarez ES, Carlson CL: Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma: Radiologic-pathologic correlation. RadioGraphics 22:911-934, 2002.

Extramedullary Hematopoiesis DEFINITION: Extramedullary hematopoiesis is a compensatory phenomenon in various diseases in which there is inadequate production or excessive destruction of blood cells. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  mooth,

Findings n O  ne

or several smooth, lobulated masses in lower chest n M  asses at multiple levels or involving entire paravertebral region Utility

n O  ften

lobulated masses situated in the lower chest n H  omogeneous soft tissue attenuation n L  arge fatty component n P  atient with congenital hemolytic anemia or thalassemia

first and only imaging modality used

CT

n A  ssociated

n H  omogeneous

with congenital hemolytic anemia (usually hereditary spherocytosis) or thalassemia (thalassemia major or intermedia) n F  atty replacement as result of adipocytic metaplasia after resolution of underlying hemolytic disorder

Utility

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

Findings

soft tissue attenuation fatty component occasionally evident n W  idening of ribs as a result of expansion of medullary cavity n L  acy appearance of vertebrae n A  bsence of bone erosion n L  arge

n S  uperior

to radiography in demonstrating presence of paravertebral masses consistent with extramedullary hematopoiesis

Nuclear Medicine Findings n U  ptake

within mass in majority of cases on bone marrow scintigraphy

Utility

n S  pecific

diagnosis can often be made on bone marrow scintigraphy

CLINICAL PRESENTATION n C  ongenital

hemolytic anemia (usually hereditary spherocytosis) or thalassemia (thalassemia major or intermedia)

n M  ost

common sites of extramedullary hematopoiesis are liver and spleen. n S  eldom evident in paravertebral region.

Suggested Readings Castelli R, Graziadei G, Karimi M, Cappellini MD: Intrathoracic masses due to extramedullary hematopoiesis. Am J Med Sci 328:299-303, 2004. Hennessy OF, Salanitri JC: Computed tomography of intrathoracic extramedullary haematopoiesis occurring as a complication of osteopetrosis. Australas Radiol 49:430-432, 2005. Kakite S, Tanabe Y, Kinoshita F, et al: Clinical usefulness of In-111 chloride and Tc-99m Sn colloid scintigraphy in the diagnosis of intrathoracic extramedullary hematopoiesis. Ann Nucl Med 19:317-320, 2005. Martin J, Palacio A, Petiti J, Martin C: Fatty transformation of thoracic extramedullary hematopoiesis following splenectomy: CT features. J Comput Assist Tomogr 14:477-478, 1990. Psichoglou H, Malagarl K, Spanomichos G: Mediastinal extramedullary hematopoiesis in hemolytic anemia. JBR-BTR 87:150-151, 2004.

PATHOLOGY n C  ompensatory

phenomenon in various diseases in which there is inadequate production or excessive destruction of blood cells

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

686

n Associated

with congenital hemolytic anemia (usually hereditary spherocytosis) or thalassemia (thalassemia major or intermedia) n Specific diagnosis can often be made on bone marrow scintigraphy

PARAVERTEBRAL MASSES

Figure 1.  Extramedullary hematopoiesis in a 39-year-old man. Posteroanterior chest radiograph shows displacement of paraspinal interfaces (arrows).

Extramedullary Hematopoiesis    687

Figure 2.  Extramedullary hematopoiesis in a 39-year-old man. Transverse unenhanced CT scan obtained at level of liver dome shows bilateral, homogeneous, isoattenuation, paravertebral, soft tissue lesions (arrows). Also note bilateral pleural effusions and increased attenuation in liver due to hemosiderosis and splenomegaly.

Meningocele or Meningomyelocele DEFINITION: Meningocele and meningomyelocele are rare anomalies that consist of herniation of the leptomeninges through an intervertebral foramen. IMAGING

DIAGNOSTIC PEARLS

Radiography

n C  ontinuity

Findings

n W  ell-demarcated mass, with round or elliptical, smooth

margins.

Utility

n A  bnormality

n R  adiographic

tumor

often first detected on the radiograph findings similar to those of neurogenic

between the cerebrospinal fluid in the thecal sac and the meningocele n E  nlargement of the intervertebral foramen n M  eningocele: contains cerebrospinal fluid only n M  eningomyelocele: contains neural tissue n M  ajority of patients have neurofibromatosis

CT

Findings

n C  ontinuity

between cerebrospinal fluid in thecal sac and meningocele n K  yphoscoliosis and meningocele usually at apex of curvature on its convex side n E  nlargement of intervertebral foramen n A  ssociated vertebral and rib anomalies common Utility n C  T

usually diagnostic

MRI

Findings

between cerebrospinal fluid in thecal sac and meningocele

PATHOLOGY n M  eningocele

and meningomyelocele are rare anomalies that consist of herniation of leptomeninges through an intervertebral foramen. n M  eningocele contains cerebrospinal fluid only, whereas meningomyelocele also contains neural tissue. n A  bnormalities occur slightly more often on right side than on the left and are situated anywhere between thoracic inlet and diaphragm.

n C  ontinuity

Utility

n D  iagnostic

method of choice; provides best visualization of spinal cord, meninges, and adjacent structures

CLINICAL PRESENTATION n P  ain

and neurologic symptoms

DIFFERENTIAL DIAGNOSIS n N  erve

sheath tumors (neurilemoma, neurofibroma, and malignant nerve sheath tumor) n S  ympathetic ganglia tumors (ganglioneuromas, ganglioneuroblastomas, and neuroblastomas)

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n A  pproximately

75% of patients present between ages of 30-60 years. n S  ixty percent to 80% of patients have neurofibromatosis.

Suggested Readings Cabooter M, Bogaerts Y, Javaheri S, et al: Intrathoracic meningnocele. Eur J Respir Dis 63:347-350, 1982. Glazer HS, Siegel MJ, Sagel SS: Low-attenuation mediastinal masses on CT. AJR Am J Roentgenol 152:1173-1177, 1989. Rainov NG, Heidecke V, Burkert W: Thoracic and lumbar meningocele in neurofibromatosis type 1: Report of two cases and review of the literature. Neurosurg Rev 18:127-134, 1995. Strollo DC, Rosado-de-Christenson ML, Jett JR: Primary mediastinal tumors: II. Tumors of the middle and posterior mediastinum. Chest 112:1344-1357, 1997.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Association



n Majority



688

with vertebral and rib anomalies is common and should suggest the diagnosis. of patients have neurofibromatosis. n MRI is the diagnostic method of choice.

PARAVERTEBRAL MASSES

Meningocele or Meningomyelocele    689

Figure 1.  Meningocele in a 29-year-old man. Posteroanterior chest radiograph shows paraspinal mass (arrows) at level of T10.

Figure 2.  Meningocele in a 29-year-old man. Lateral chest radiograph shows paraspinal mass (arrows) at level of T10.

Figure 3.  Meningocele in a 29-year-old man. CT scan demonstrates characteristic fluid attenuation of meningocele, which communicates with the thecal sac (arrows).

DIAPHRAGM

Part 65 

Bilateral Elevation of the Diaphragm DEFINITION: Both hemidiaphragms may become elevated. IMAGING

DIAGNOSTIC PEARLS

Radiography

n B  ilateral

Findings

n B  ilateral

elevation of diaphragm show likely cause, including pleural disease, obesity, and hepatosplenomegaly

n M  ay

Utility

n C  hest

radiograph is first imaging modality used. inspiratory effort or expiratory radiograph may mimic bilateral elevation of diaphragm.

n P  oor

Fluoroscopy Findings

n B  ilateral

elevation of diaphragm

n B  ilateral phrenic nerve palsy: paradoxical upward motion

of both hemidiaphragms during inspiratory effort or sniff usually observed on fluoroscopic examination n C  ephalad movement of paralyzed diaphragm during inspiration accompanied by outward chest wall and inward abdominal wall motion (“thoracoabdominal paradox”) Utility

n C  ephalad

movement of ribs in response to accessory muscles contraction may give false appearance of caudad displacement of diaphragm. n D  espite this potential pitfall, fluoroscopy can be effectively used to evaluate condition.

CT

Findings

n B  ilateral

elevation of diaphragm show causes, including pleural disease, obesity, hepatosplenomegaly, ascites, abdominal neoplasm, and bilateral subphrenic abscess

n M  ay

Utility

n S  uperior

causes

elevation of diaphragm upward motion of both hemidiaphragms during an inspiratory effort or sniff n C  haracteristic findings: cephalad movement of paralyzed diaphragm during inspiration n E  levated diaphragm with normal diaphragmatic motion possibly due to obesity, bilateral fibrothorax, hepatosplenomegaly, ascites, abdominal neoplasm, bilateral subphrenic abscess, or pregnancy n P  aradoxical

to radiography in demonstrating underlying

MRI

Findings

n B  ilateral

elevation of diaphragm diaphragmatic motion

n A  bnormal

Utility n C  an

assess normal and abnormal diaphragmatic motion and diaphragmatic paralysis n S  eldom used in evaluation of patients

Ultrasonography Findings

n B  ilateral

elevation of diaphragm diaphragmatic motion n M  ay show causes, including hepatosplenomegaly, ascites, abdominal neoplasm, and bilateral subphrenic abscess n A  bnormal

Utility n C  an

assess normal and abnormal diaphragmatic motion and diaphragmatic paralysis n H  as ability to assess diaphragmatic thickness and changing thickness with respiration, which makes it possibly superior to fluoroscopy

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Common



n Radiologic



n Causes

692

causes are spinal cord injury and generalized neuromuscular syndromes. and fluoroscopic findings show elevation of both hemidiaphragms with paradoxical motion on

sniff test. of bilateral elevation of normal diaphragm include poor inspiratory effort, obesity, bilateral ­fibrothorax, hepatosplenomegaly, ascites, abdominal neoplasm, and bilateral subphrenic abscess.

Bilateral Elevation of the Diaphragm    693

DIAPHRAGM

Figure 1.  Bilateral elevation of diaphragm in obesity. Anteroposterior chest radiograph in a patient on long-term corticosteroid therapy shows bilateral elevation of the diaphragm, widening of the mediastinum, and apparent enlargement of the cardiopericardial silhouette.

CLINICAL PRESENTATION n P  atients

usually have respiratory symptoms consisting mainly of dyspnea and orthopnea.

DIFFERENTIAL DIAGNOSIS n S  pinal

cord injury n B  ilateral fibrothorax n A  scites n H  epatosplenomegaly n A  bdominal neoplasm n S  ystemic lupus erythematosus n P  regnancy n O  besity

PATHOLOGY n B  ilateral

diaphragmatic palsy causes bilateral diaphragm elevation, which is, in turn, caused by spinal cord injury and generalized neuromuscular syndromes. n C  auses of bilateral elevation of normal diaphragm include poor inspiratory effort, obesity, bilateral ­fibrothorax, hepatosplenomegaly, ascites, abdominal

Figure 2.  Bilateral elevation of diaphragm in obesity. Coronal reformatted image from a multidetector CT scan in the same patient as in Figure 1 demonstrates extensive mediastinal lipomatosis and increased size of the cardiophrenic fat pads. The heart size is within normal limits.

neoplasm, bilateral subphrenic abscess, and pregnancy.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n B  ilateral

elevation of diaphragm is uncommon. common cause of bilateral phrenic nerve palsy is spinal cord injury.

n M  ost

Suggested Readings Celli BR: Respiratory management of diaphragm paralysis. Semin Respir Crit Care Med 23:275-281, 2002. Eren S, Ciris F: Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol 54:448-459, 2005. Gierada DS, Slone RM, Fleishman MJ: Imaging evaluation of the diaphragm. Chest Surg Clin North Am 8:237-280, 1998. Mirvis SE: Imaging of acute thoracic injury: The advent of MDCT screening. Semin Ultrasound CT MR 26:305-331, 2005. Sliker CW: Imaging of diaphragm injuries. Radiol Clin North Am 44:199-211, 2006.

Unilateral Elevation of the Diaphragm DEFINITION: Unilateral elevation of the diaphragm may be due to phrenic nerve palsy, diaphragmatic eventration, or due to intrathoracic or intra-abdominal abnormalities. IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  aralyzed

Findings n W  ith

paralysis or eventration the hemidiaphragm is elevated, with accentuated dome configuration in both posteroanterior and lateral projections. n P  artial eventration usually involves anteromedial portion of right hemidiaphragm. Utility

n T  umor

hemidiaphragm is elevated and has an accentuated dome configuration in both posteroanterior and lateral projections. n W  ith unilateral diaphragmatic paralysis there is paradoxical upward motion of the affected side. n E  levated normal diaphragm occurs secondary to decreased lung volume, splinting of diaphragm, or intra-abdominal contents (e.g., an abdominal mass) pushing hemidiaphragm upward.

invasion or compression of phrenic nerve may be suspected on radiography but usually requires confirmation with CT. n M  imics of elevated hemidiaphragm on the radiograph include subpulmonic effusion and diaphragmatic hernia.

n T  umor,

Fluoroscopy

Utility

Findings n P  hrenic

nerve palsy: paradoxical upward motion of affected side consisting of reverse excursion of at least 2 cm indicates phrenic nerve palsy n E  ventration: initial inspiratory lag or small paradoxical motion (but downward motion later in inspiration) Utility

n M  ost

reliable maneuver for detecting hemidiaphragmatic paralysis is sniff test performed while visualizing the diaphragm with fluoroscopy or ultrasonography. n S  niff test is positive in over 90% of patients with unilateral phrenic nerve palsy. n F  alse-negative results can occur if patient uses abdominal musculature to elevate diaphragm during expiratory phase of breathing.

CT

Findings

n H  emidiaphragm

is elevated. eventration, a thin diaphragm is seen as a continuous layer above elevated abdominal viscera and retroperitoneal or omental fat.

n I n

lymph node, or another mass may be compressing the phrenic nerve or the diaphragm.

n H  elpful

in differentiating diaphragmatic paralysis or eventration from other causes of elevation of hemidiaphragm (e.g., abdominal mass or cyst)

MRI

Findings

n E  levation

Utility

of hemidiaphragm

n S  eldom

indicated normal and abnormal motion and paralysis of diaphragm

n D  etects

Ultrasonography Findings n P  hrenic

nerve palsy: paradoxical upward motion of affected side consisting of reverse excursion of at least 2 cm n E  ventration: initial inspiratory lag or small paradoxical motion (but downward motion later in inspiration) Utility n C  an

assess normal and abnormal diaphragmatic motion and diaphragmatic paralysis

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Common



n Most



694

causes: invasion of phrenic nerve by tumor or trauma reliable maneuver for detecting hemidiaphragmatic paralysis: sniff test done while visualizing diaphragm with fluoroscopy or ultrasonography. n Thoracic causes of elevation of normal hemidiaphragm: atelectasis, splinting of diaphragm due to acute process (e.g., fractured rib, pleurisy, pneumonia) or after surgery (e.g., lobectomy, pneumonectomy) n Abdominal causes of elevation of normal hemidiaphragm: distended stomach, interposition of colon between liver and right hemidiaphragm (Chilaiditi syndrome), subphrenic abscess, hepatomegaly, and abdominal neoplasm

DIAPHRAGM

Figure 1.  Posteroanterior chest radiograph shows marked elevation of the left hemidiaphragm. Minimal linear atelectasis is also present in the left lung base. Note that costophrenic and costovertebral sulci are deepened, narrowed, and sharpened, a feature best seen on the frontal view. Fluoroscopy demonstrated paradoxical motion of the left hemidiaphragm. The patient was a 44-year-old man with idiopathic left phrenic nerve palsy.

Unilateral Elevation of the Diaphragm    695

Figure 2.  Eventration of right hemidiaphragm. Chest radiograph shows marked elevation of the right hemidiaphragm. The appearance is indistinguishable from phrenic nerve palsy. The patient was a 65-year-old man.

Figure 4.  Elevation of hemidiaphragm due to abdominal abnormality. In the same patient as Figure 3, CT image demonstrates liver cysts resulting in increased size of the liver and elevation of the right hemidiaphragm. The patient was an 82-year-old woman.

Figure 3.  Elevation of hemidiaphragm due to abdominal lesion. Chest radiograph shows elevation of the right hemidiaphragm. The patient was an 82-year-old woman with liver cyst.

696    Unilateral Elevation of the Diaphragm

n H  as

ability to assess diaphragmatic thickness and changing thickness with respiration, which makes it possibly superior to fluoroscopy

CLINICAL PRESENTATION n P  atients

are usually asymptomatic. is usually found as incidental finding in patients undergoing chest radiography for other reasons. n D  yspnea with mild to moderate effort may develop in patients with underlying lung disease. n A  bnormality

DIAPHRAGM

n T  horacic

causes of elevation of normal hemidiaphragm include atelectasis, splinting of diaphragm due to acute process (e.g., fractured rib, pleurisy, pneumonia) or after surgery (e.g., lobectomy, pneumonectomy). n A  bdominal causes of elevation of normal hemidiaphragm include distended stomach, interposition of colon between liver and right hemidiaphragm (Chilaiditi syndrome), subphrenic abscess, hepatomegaly, and abdominal neoplasm.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ost

DIFFERENTIAL DIAGNOSIS n P  hrenic

nerve palsy eventration n H  epatomegaly n P  leurisy n L  obectomy n P  neumonectomy n A  bdominal neoplasm n D  istended stomach n D  iaphragmatic

common cause of phrenic nerve palsy is compression or invasion of nerve by neoplasm, which accounts for approximately 30% of cases. n O  ther common causes include trauma (natural or surgical) and phrenic “frostbite” after cardiac surgery. n L  ess common causes include herpes zoster, cervical spondylosis, poliomyelitis, and pneumonia. n H  owever, in many cases of phrenic nerve palsy, etiology is unknown. n U  nilateral diaphragmatic elevation may also be due to eventration of diaphragm.

Suggested Readings

PATHOLOGY n M  ost

common cause of phrenic nerve palsy is compression or invasion of nerve by neoplasm. n O  ther causes include trauma (natural or surgical) and phrenic “frostbite” after cardiac surgery. n H  erpes zoster, cervical spondylosis, poliomyelitis, and pneumonia may also be causative. n E  ventration may occur.

Celli BR: Respiratory management of diaphragm paralysis. Semin Respir Crit Care Med 23:275-281, 2002. Eren S, Ciris F: Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol 54:448-459, 2005. Gierada DS, Slone RM, Fleishman MJ: Imaging evaluation of the diaphragm. Chest Surg Clin N Am 8:237-280, 1998. Mirvis SE: Imaging of acute thoracic injury: The advent of MDCT screening. Semin Ultrasound CT MR 26:305-331, 2005. Sliker CW: Imaging of diaphragm injuries. Radiol Clin North Am 44:199-211, 2006.

Phrenic Nerve Palsy DEFINITION: Phrenic nerve palsy may be due to injury, invasion, or compression of the phrenic nerve and results in paralysis of the ipsilateral hemidiaphragm. IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  aralyzed

Findings

n P  aralyzed

hemidiaphragm is elevated, with accentuated dome configuration in both posteroanterior and lateral projections. n C  ostophrenic and costovertebral sulci tend to be deepened, narrowed, and sharpened. n W  ith left-sided paralysis, stomach and splenic flexure of colon relate to hemidiaphragm and contain more gas than normal.

hemidiaphragm is elevated and with an accentuated dome configuration in posteroanterior and lateral projections. n W  ith unilateral diaphragmatic paralysis there is paradoxical upward motion of the affected side. n P  aradoxical motion should consist of a reverse excursion of at least 2 cm to be consistent with diaphragmatic paralysis.

Utility

n T  umor

invasion or compression of phrenic nerve may be suspected on radiography but usually requires confirmation with CT.

Fluoroscopy Findings

n P  aradoxical

upward motion of affected side consisting of reverse excursion of at least 2 cm during deep inspiration and sniff test.

Utility

n M  ost

reliable maneuver for detecting hemidiaphragmatic paralysis is sniff test performed while visualizing diaphragm with fluoroscopy or ultrasonography. n S  niff test is positive in over 90% of patients with unilateral phrenic nerve palsy. n F  alse-negative results can occur if patient uses abdominal musculature to elevate diaphragm during expiratory phase of breathing.

CT

Findings

n E  levation

Utility

of diaphragm

to rule out tumor, lymph node, or other mass that may be compressing the phrenic nerve n H  elpful in differentiating diaphragmatic paralysis or eventration from other causes of hemidiaphragm elevation such as abdominal mass or cyst

MRI

n E  levation

n S  eldom

indicated normal and abnormal motion and paralysis of diaphragm

n D  etects

Ultrasonography Findings

n P  aradoxical

upward motion of affected side consisting of reverse excursion of at least 2 cm

Utility

n A  ssesses

normal and abnormal diaphragmatic motion and diaphragmatic paralysis n H  as ability to assess diaphragmatic thickness and changing thickness with respiration, possibly making it superior to fluoroscopy

CLINICAL PRESENTATION n W  ith

n U  sed

Findings

Utility

unilateral phrenic nerve palsy, patients are usually asymptomatic. n A  bnormality is usually found as an incidental finding in patients undergoing chest radiography for other reasons. n D  yspnea with mild to moderate effort may develop in patients with underlying lung disease. n W  ith bilateral phrenic nerve palsy, patients usually have severe respiratory symptoms consisting mainly of dyspnea and orthopnea.

of diaphragm

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n C  ommon



n R  adiologic



causes include invasion of phrenic nerve by tumor, trauma, or spinal cord injury. findings include elevation of the hemidiaphragm or hemidiaphragms. n P  aradoxical motion on sniff test is performed while visualizing the diaphragm with fluoroscopy or ­ultrasonography. n P  ositive sniff test requires reverse excursion of at least 2 cm.

697

698    Phrenic Nerve Palsy

Figure 1.  Phrenic nerve palsy. Posteroanterior chest radiograph shows marked elevation of the left hemidiaphragm. Minimal linear atelectasis is also present in the left lung base. Note that costophrenic and costovertebral sulci are deepened, narrowed, and sharpened, a feature best seen on the frontal view. Fluoroscopy demonstrated paradoxical motion of the left hemidiaphragm. The patient was a 44-year-old man with idiopathic left phrenic nerve palsy.

Figure 3.  Phrenic nerve palsy due to lung cancer. Chest radiograph shows elevation of the left hemidiaphragm and mass (arrow) adjacent to the aorticopulmonary window. The patient was a 54-year-old woman with phrenic nerve palsy due to lung cancer.

DIAPHRAGM

Figure 2.  Phrenic nerve palsy. Lateral chest radiograph shows marked elevation of the left hemidiaphragm. Minimal linear atelectasis is also present in the left lung base. Note that costophrenic and costovertebral sulci are deepened, narrowed, and sharpened, a feature best seen on the frontal view (see Fig. 1). Fluoroscopy demonstrated paradoxical motion of the left hemidiaphragm. The patient was a 44-year-old man with idiopathic left phrenic nerve palsy.

Figure 4.  Phrenic nerve palsy due to lung cancer. In the same patient as Figure 3, CT image demonstrates mass (arrows) invading the mediastinum at the region of the phrenic nerve and aorticopulmonary window. The patient was a 54-year-old woman with phrenic nerve palsy due to lung cancer.

Phrenic Nerve Palsy    699

DIAPHRAGM

DIFFERENTIAL DIAGNOSIS n D  iaphragmatic n D  iaphragmatic n H  epatomegaly n F  ibrothorax

n S  ubpulmonic

eventration hernia

pleural effusion

n O  ther

common causes include trauma (natural or surgical) and phrenic “frostbite” after cardiac surgery. n L  ess common causes include herpes zoster, cervical spondylosis, poliomyelitis, and pneumonia. n H  owever, in many cases the etiology is unknown. n F  or bilateral phrenic nerve palsy, the most common cause is spinal cord injury.

Suggested Readings

PATHOLOGY n C  aused

by compression or invasion of nerve by neoplasm n O  ther causes include trauma (natural or surgical) and phrenic “frostbite” after cardiac surgery n M  ay also be due to herpes zoster, cervical spondylosis, poliomyelitis, and pneumonia

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ost

common cause is compression or invasion of nerve by neoplasm, which accounts for approximately 30% of cases.

Celli BR: Respiratory management of diaphragm paralysis. Semin Respir Crit Care Med 23:275-281, 2002. Gierada DS, Slone RM, Fleishman MJ: Imaging evaluation of the diaphragm. Chest Surg Clin North Am 8:237-280, 1998.

Diaphragmatic Eventration DEFINITION: Diaphragmatic eventration is failure of muscular development of part or all of one or both hemidiaphragms. IMAGING

DIAGNOSTIC PEARLS

Radiography

n R  adiologic

Findings

n E  levation

of hemidiaphragm is evident. partial eventration, affected hemidiaphragm shows smaller than normal inspiratory excursion/ n U  sually the anteromedial portion of the right hemidiaphragm is involved. n W  ith

Utility

n E  ventration

is usually first detected by radiography.

signs of complete eventration of a hemidiaphragm are identical to those of diaphragmatic paralysis consisting of elevation of hemidiaphragm. n W  ith partial eventration, affected hemidiaphragm shows a smaller than normal inspiratory excursion. n O  n fluoroscopy, there may be an initial inspiratory lag or small paradoxical motion; however, later in inspiration there is downward motion.

Fluoroscopy Findings n I nitial

inspiratory lag or small paradoxical motion can be seen; however, later in inspiration it has a downward motion.

Utility

n H  elpful

in distinguishing eventration from diaphragmatic paralysis

Ultrasonography Findings

n D  iaphragm

may show an initial inspiratory lag or small paradoxical motion; however, later in inspiration it has a downward motion.

Utility

n A  bility

of ultrasonography to assess diaphragmatic thickness and changing thickness with respiration makes it possibly superior to fluoroscopy.

CT

Findings

n T  hin diaphragm is seen as continuous layer above elevated

DIFFERENTIAL DIAGNOSIS n D  iaphragmatic n D  iaphragmatic n H  epatomegaly n S  ubpulmonic

palsy hernia

pleural effusion

PATHOLOGY n T  here

is congenital failure of muscular development of part or all of one or both hemidiaphragms. n T  otally eventrated hemidiaphragm consists of membranous sheet attached peripherally to normal muscle at points of origin from rib cage. n T  otal eventration occurs almost exclusively on left side. n P  artial eventration is usually present in anteromedial portion of right hemidiaphragm. n P  artial eventration rarely occurs on the left and occasionally in central portion of either cupola.

abdominal viscera and retroperitoneal or omental fat.

Utility

n M  ain

role in partial eventration is distinguishing abnormality from focal bulge in diaphragmatic contour caused by tumor or hernia.

CLINICAL PRESENTATION n E  ventration

is typically asymptomatic. may be present in obese patients as a result of raised intra-abdominal pressure.

n S  ymptoms

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n C  omplete

eventration of hemidiaphragm is always congenital. n P  artial eventration is more common than total form, seen in patients older than age 60 years, and may be acquired. n P  artial eventration occurs with equal frequency in men and women.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

700

n Unilateral

and partial eventration when seen in adults typically involves the anteromedial portion of the right hemidiaphragm. n Radiologically, complete eventration of hemidiaphragm is identical to diaphragmatic paralysis and consists of elevation of the hemidiaphragm. n Distinction of eventration from diaphragmatic paralysis can usually be made during fluoroscopy (“sniff test”) or ultrasonography.

DIAPHRAGM

Figure 1.  Eventration of right hemidiaphragm. Chest radiograph shows marked elevation of the right hemidiaphragm. The appearance is indistinguishable from phrenic nerve palsy. The patient was a 65-year-old man.

Diaphragmatic Eventration    701

Figure 2.  Partial eventration of the right hemidiaphragm. Posteroanterior chest radiograph demonstrates focal elevation (arrows) of the anteromedial portion of the right hemidiaphragm characteristic of partial eventration. The patient was a 51-yearold woman.

Figure 3.  Partial eventration of the right hemidiaphragm. In the same patient as Figure 2, lateral chest radiograph demonstrates focal elevation (arrows) of the anteromedial portion of the right hemidiaphragm characteristic of partial eventration. The patient was a 51-yearold woman.

Suggested Readings Deslauriers J: Eventration of the diaphragm. Chest Surg Clin North Am 8:315-330, 1998. Gierada DS, Slone RM, Fleishman MJ: Imaging evaluation of the diaphragm. Chest Surg Clin North Am 8:237-280, 1998.

Verhey PT, Gosselin MV, Primack SL, et al: Differentiating diaphragmatic paralysis and eventration. Acad Radiol 14:420-425, 2007.

Hiatal Hernia DEFINITION: A hiatal hernia is a hernia through the esophageal hiatus of the diaphragm into the ­thorax.

IMAGING

DIAGNOSTIC PEARLS

Radiography

n H  iatal

Findings n H  iatal

hernia typically manifests radiographically as a retrocardiac mass, usually containing air or air-fluid level. n A  large mass may contain a double air-fluid level. n I n cases in which most of stomach has herniated through hiatus, the stomach may undergo volvulus. n O  ther structures, such as portion of transverse colon, omentum, or liver, may also be seen. n S  igns of strangulation of herniated contents are evident. Utility

n L  arge

hernia typically manifests radiographically as a retrocardiac mass, usually containing air or an air-fluid level. n E  sophageal hernias usually result from widening of esophageal hiatus, allowing stomach and omentum to protrude into chest. n O  ther structures, such as portion of transverse colon, omentum, or liver, may also be seen. n E  sophageal hernias are evident on CT in 5% of individuals younger than 40 years, 30% of those aged 40-49, and 65% of those aged 60-79.

hiatus hernias can usually be readily recognized.

CT

PATHOLOGY

Findings

n W  idening

of esophageal hiatus allows stomach and omentum to protrude into chest n N  ormally, esophageal hiatus is elliptical and measures ≤15 mm in width Utility

n M  ultidetector

CT with coronal and sagittal reformatted images is most effective and useful imaging technique in assessing diaphragmatic hernias.

n H  erniation

of diaphragm occurs through esophageal hiatus into thorax. n H  iatal hernias may be sliding or paraesophageal. n S  liding hernias are the most common; the hernia slides back and forth between the abdominal and chest cavities. n I n paraesophageal hernias part of the stomach bulges into the thorax and remains there.

MRI

Findings

n W  idening

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY

Utility

n P  revalence

of esophageal hiatus allows stomach and omentum to protrude into chest.

n D  iagnosis

can be readily made with MRI, but use of this modality is rarely indicated.

CLINICAL PRESENTATION n M  ost

diaphragmatic hernias do not give rise to symptoms. n P  atients with symptomatic hiatal hernia may present with heartburn and regurgitation. n O  ccasionally, chronic reflux may result in scarring and narrowing of lower esophagus and symptoms of esophageal obstruction. n I n cases in which most of stomach has herniated through hiatus, it may undergo volvulus and strangulation may occur.

of esophageal hiatal hernias increases with age. n T  hey are evident on CT in approximately 5% of individuals younger than 40 years, 30% of those aged 40-59, and 65% of those aged 60-79.

Suggested Readings Abbara S, Kalan MM, Lewicki AM: Intrathoracic stomach revisited. AJR Am J Roentgenol 181:403-414, 2003. Canon CL, Morgan DE, Einstein DM, et al: Surgical approach to gastroesophageal reflux disease: What the radiologist needs to know. RadioGraphics 25:1485-1499, 2005. Eren S, Ciris F: Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol 54:448-459, 2005.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Prevalence



n Patients



702

increases with age. are usually asymptomatic. n Strangulation of hernial contents may occur.

DIAPHRAGM

Hiatal Hernia    703

Figure 1.  Hiatal hernia. Posteroanterior chest radiograph demonstrates large retrocardiac mass with fluid level. The appearance is characteristic of a hiatal hernia. The patient was an 85-year-old woman.

Figure 2.  Hiatal hernia. In the same patient as Figure 1, lateral chest radiograph demonstrates large retrocardiac mass with fluid level. The appearance is characteristic of a hiatal hernia. The patient was an 85-year-old woman.

Figure 3.  Hiatal hernia. CT image shows herniation of stomach and omentum into the retrocardiac region. The patient was a 79-year-old man.

Figure 4.  Hiatal hernia. In the same patient as Figure 3, CT image at the level of the esophageal hiatus shows widening of the space between the right and left crura (arrows) and hiatal hernia. The patient was a 79-year-old man.

Bochdalek Hernia DEFINITION: A Bochdalek hernia is herniation of omentum and abdominal viscera into the chest through a defect in the posterolateral aspect of the diaphragm. IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  anifests

Findings n T  hese

lesions manifest as a focal bulge in the hemidiaphragm or as a mass adjacent to the posteromedial aspect of either hemidiaphragm. n P  revalence increases with age; they may manifest in patients with previously normal radiographs. Utility

n D  iagnosis

can often be suspected on radiography by typical location and by lower density than soft tissue of mass. n A  ppearance can mimic that of pulmonary, mediastinal, or paravertebral masses.

CT

as a focal bulge in hemidiaphragm or as a mass adjacent to posteromedial aspect of either hemidiaphragm n M  ay manifest in patients with previously normal radiographs n O  ccasionally may be large and contain portions of kidney and, rarely, stomach and small bowel n P  revalence increases with age n A  dult Bochdalek hernias are usually small and asymptomatic

n C  ongenital

Findings n I n

adults, results from herniation through posterior diaphragmatic defect lateral to crura. n O  ccasionally may be large and contain portions of kidney and, rarely, stomach and small bowel Utility

n D  iagnosis

is readily made on CT. CT with coronal and sagittal reformatted images is most effective and useful imaging technique in assessing diaphragmatic hernias.

Bochdalek hernias are frequently associated with pulmonary hypoplasia. n M  ost large hernias have no peritoneal sac, so communication between pleural and peritoneal cavities is wide open. n A  dult Bochdalek hernias are presumably acquired defects.

n M  ultidetector

MRI

Utility

n D  iagnosis

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n I n

of diaphragmatic hernias can be readily made.

CLINICAL PRESENTATION n I n

infants this hernia is associated with severe respiratory distress. n A  dult patients with Bochdalek hernias are usually asymptomatic. n O  ccasionally patients may complain of epigastric or lower sternal pressure and discomfort and sometimes cardiorespiratory and gastrointestinal symptoms.

PATHOLOGY n W  hen

hernia is large, almost entire abdominal contents may be in left hemithorax, interfering with normal lung development.

infants, Bochdalek hernia is most common form of diaphragmatic hernia, with incidence of 1:2000 births. n I n adults, small hernias are more common than in infants; they are seen on CT in 5%-10% of adults. n I ncidence of adult Bochdalek hernia increases with age, suggesting that they are acquired. n M  ost cases are left sided. n T  hese hernias are rare in adult patients younger than 40; they are seen in approximately 5% of patients aged 40-49 years, 15% of patients aged 50-69 years, and 35% of older patients.

Suggested Readings Eren S, Ciris F: Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol 54:448-459, 2005. Mullins ME, Stein J, Saini SS, et al: Prevalence of incidental Bochdalek’s hernia in a large adult population. AJR Am J Roentgenol 177:363-366, 2001.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n May



n Manifests

704

be congenital or acquired on radiographs as a focal bulge in the hemidiaphragm or as a mass adjacent to the posteromedial aspect of either hemidiaphragm

DIAPHRAGM

Figure 1.  Development of a Bochdalek hernia in an elderly patient. A view of the right lower chest from a posteroanterior radiograph in a 78-year-old woman is unremarkable. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Bochdalek Hernia    705

Figure 2.  Development of a Bochdalek hernia in an elderly patient. View from posteroanterior radiograph performed 5 years later than in Figure 1 demonstrates a large mass adjacent to the posteromedial aspect of the right hemidiaphragm (arrow). The mass has lower opacity than the heart and soft tissues of the abdomen, consistent with fat. The patient had no symptoms related to the hernia. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Figure 4.  Bochdalek hernia. CT image shows focal discontinuity of the left hemidiaphragm and herniation of omental fat and part of the left kidney. The patient was a 36-year-old woman with no symptoms related to the small Bochdalek hernia.

Figure 3.  Development of a Bochdalek hernia in an elderly patient. View from lateral radiograph performed 5 years later than in Figure 1 demonstrates a large mass adjacent to the posteromedial aspect of the right hemidiaphragm (arrow). The mass has lower opacity than the heart and soft tissues of the abdomen, consistent with fat. The patient had no symptoms related to the hernia. (From Müller NL, Fraser RS, Colman NC, Paré PD: Radiologic Diagnosis of Diseases of the Chest. Philadelphia, WB Saunders, 2001.)

Morgagni Hernia DEFINITION: A Morgagni hernia is a herniation through the parasternal hiatus of the diaphragm. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  mooth,

Findings n A 

smooth, well-defined homogeneous opacity is seen in the right cardiophrenic angle. n O  ccasionally, this opacity is inhomogeneous owing to either air-containing loops of bowel or fatty nature of hernial contents. n I n rare cases when the hernia penetrates into the pericardial sac, loops of air-containing bowel are identified anterior to the cardiac shadow. Utility

n O  ften

first detected incidentally on chest radiograph

CT

Findings

n H  erniation

of abdominal contents between costal and sternal attachments of diaphragm n A  nteromedial in location and usually occurs on right side n M  ajority containing only omentum, which is seen as a mass with fat attenuation n T  ransverse colon situated high in abdomen, with peak situated anteriorly and superiorly—a location that is virtually diagnostic Utility

n M  ultidetector

CT with coronal and sagittal reformatted images is most effective and useful imaging technique in assessing diaphragmatic hernias.

MRI

Findings

n H  erniation

of abdominal contents between costal and sternal attachments of diaphragm n A  nteromedial in location and usually occurs on right side Utility

of diaphragmatic hernias can be readily made on MRI, although use of this modality is seldom indicated.

well-defined, homogeneous, occasionally inhomogeneous, opacity in right cardiophrenic angle n A  nteromedial in location and occurs on the right side n T  ransverse colon situated high in abdomen, with peak situated anteriorly and superiorly—a finding that is virtually diagnostic n S  ome

patients may complain of epigastric or lower sternal pressure and discomfort and sometimes cardiorespiratory and gastrointestinal symptoms. n O  ccasionally, stomach or colon may become incarcerated or strangulated, resulting in pain and vomiting.

DIFFERENTIAL DIAGNOSIS n P  ericardial

fat pad cyst n D  iaphragmatic lipoma n P  ericardial

PATHOLOGY n H  ernia

may be developmental in origin or post-traumatic. n I n contrast to Bochdalek hernia, peritoneal sac is present in most cases. n H  ernial sac may include, in order of decreasing frequency: omentum, colon, stomach, liver, and small intestine. n L  eft foramen relates to heart; thus, most herniations are seen on right side.

n D  iagnosis

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  orgagni

CLINICAL PRESENTATION n A  dult

patients with Morgagni hernia are often asymptomatic.

(parasternal) hernia is uncommon. are more common in adults than children. n T  hey are often associated with obesity or other situations involving increased intra-abdominal pressure such as severe effort or trauma. n H  ernias

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n This



n Some



706

uncommon hernia is associated with obesity or trauma and usually asymptomatic. patients may complain of epigastric or lower sternal pressure and discomfort and sometimes cardiorespiratory and gastrointestinal symptoms. n Occasionally stomach or colon may become incarcerated or strangulated, resulting in pain and vomiting. n Diagnosis can be readily confirmed on CT.

DIAPHRAGM

Morgagni Hernia    707

Figure 1.  Morgagni hernia. Posteroanterior chest radiograph demonstrates a mass in the right costophrenic sulcus. The mass has a density lower than that of soft tissue, consistent with fat. The patient was a 49-year-old man. Figure 2.  Morgagni hernia. In the same patient as Figure 1, lateral chest radiograph demonstrates a mass in the right costophrenic sulcus. The mass has a density lower than that of soft tissue, consistent with fat. The patient was a 49-year-old man.

Figure 3.  Morgagni hernia. In the same patient as Figure 1, CT image demonstrates omentum and omental vessels (arrows) herniating through the right lower parasternal region diagnostic of Morgagni hernia. The patient was a 49-year-old man. Figure 4.  Morgagni hernia. Sagittal reformatted image demonstrates anterior herniation (arrow) of omentum and large bowel into the chest. The findings are characteristic of Morgagni hernia. The patient was a 54-year-old man.

Suggested Readings Eren S, Ciris F: Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol 54:448-459, 2005. Loong TP, Kocher HM: Clinical presentation and operative repair of hernia of Morgagni. Postgrad Med J 81(951):41-44, 2005.

Mirvis SE: Imaging of acute thoracic injury: The advent of MDCT screening. Semin Ultrasound CT MR 26:305-331, 2005. Sliker CW: Imaging of diaphragm injuries. Radiol Clin North Am 44:199-211, 2006.

Part 66 

CHEST WALL

Deformities of Chest Wall DEFINITION: Congenital and developmental anomalies may affect the chest wall. IMAGING

DIAGNOSTIC PEARLS

Radiography

n P  oland

Findings n P  oland

syndrome: unilateral hyperlucency with absent axillary fold on the affected side, sometimes associated with rib deformities n P  ectus excavatum: obscured right-sided heart border, heart displaced to left and rotated, and spurious cardiomegaly n P  ectus excavatum: depression and deformity in lower portion of sternum n P  ectus carinatum: anterior prominence of sternum n K  yphoscoliosis: curvature usually convex to the right n C  ongenital rib anomalies (most commonly cervical rib) n R  ib notching: most commonly due to neurogenic tumor or coarctation of aorta Utility n I n

severe kyphoscoliosis, chest radiograph is difficult to evaluate because of rotation of the thorax and heart.

CT

Findings n P  oland

syndrome: absence/hypoplasia of pectoral girdle musculature, with absent sternocostal head of pectoralis major and chest wall defects n P  ectus excavatum: depression and deformity of the lower sternum, with associated compression of lungs Utility n B  est

quantifies severity of pectus excavatum

MRI

Findings

syndrome: absence/hypoplasia of pectoral girdle musculature, with absent sternocostal head of pectoralis major and chest wall defects

syndrome: unilateral hyperlucency with absent axillary fold on the affected side and sometimes associated with rib deformities n P  ectus excavatum: obscured right-sided heart border, heart displaced to left and rotated, and spurious cardiomegaly n P  ectus excavatum: lower portion of sternum shows depression and deformity n P  ectus carinatum: anterior prominence of sternum n K  yphoscoliosis: abnormal posterior and lateral thoracic curvature

CLINICAL PRESENTATION n P  oland

syndrome is associated with increased incidence of leukemia, non-Hodgkin lymphoma, lung cancer, and breast cancer; majority of patients present with cosmetic complaints, but in other cases the presentation varies according to the type of defect. n P  ectus excavatum is usually asymptomatic or presents as chest/back pain; it is associated with increased frequency of other congenital anomalies. n P  ectus carinatum is usually asymptomatic although may have arrhythmias or dyspnea; physical examination can establish the diagnosis. n K  yphoscoliosis is abnormal posterior and lateral thoracic curvature, 80% of which is idiopathic, or with associated congenital causes. n C  ervical ribs cause thoracic outlet syndrome in less than 10% of patients.

n P  oland

Utility

n M  odality

of choice for assessment of chest wall soft tissue abnormalities

DIFFERENTIAL DIAGNOSIS n P  oland

syndrome excavatum n P  ectus carinatum n P  ectus

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

708

n Cross-sectional

imaging techniques enable precise localization of chest wall lesions and, in some cases, definitive diagnosis. n Most common chest wall deformity is pectus excavatum (90%), followed by pectus carinatum (5%-7%). n MRI is the imaging modality of choice for assessment of chest wall soft tissue abnormalities.

CHEST WALL

Figure 1.  Poland syndrome. Anteroposterior chest radiograph shows hyperlucency of the left hemithorax compared with contralateral side. Two hypoplastic ribs are present in the ipsilateral hemithorax (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Deformities of Chest Wall    709

Figure 2.  Pectus excavatum in a 22-year-old woman. Posteroanterior chest radiograph shows obscuration of the rightsided heart border (arrows) and displacement of the heart to the left. (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Figure 4.  Pectus excavatum in a 22-year-old woman. In the same patient as Figure 2, CT scan demonstrates severe pectus excavatum with compression of the lungs and displacement of the heart to the left. (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Figure 3.  Pectus excavatum in a 22-year-old woman. In the same patient as Figure 2, lateral chest radiograph shows posterior displacement of the sternum (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

710    Deformities of Chest Wall

n K  yphoscoliosis n R  ight

middle lobe atelectasis n C  ardiomegaly n T  rauma

PATHOLOGY n P  oland

syndrome is absence/hypoplasia of pectoral girdle musculature, with absent sternocostal head of pectoralis major and chest wall defects. n P  ectus excavatum generally present at birth and is progressive with increasing depth of sternal depression as the patient grows. n K  yphoscoliosis, when severe, causes decreased compliance of lung and chest wall, with resultant restrictive lung disease. n R  ib notching results from rib erosion by dilated intercostal arteries taking part in collateral arterial flow such as in aortic coarctation and affects the lower margin of one or more ribs.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n P  oland

syndrome: three times more common in males than in females and involves the right side in 75% of patients

CHEST WALL

n P  ectus

excavatum: most common disorder of chest wall formation (1 case/300-400 live births), with 3:1 male-to-female ratio n P  ectus carinatum: less frequent than pectus excavatum (5%-7% vs. 90%), with 4:1 male-to-female ratio and positive familial predisposition n C  ongenital rib anomalies: found in 1%-2% of chest radiographs and are isolated findings occurring sporadically and lacking clinical significance n C  ervical rib: present in about 0.5% of the general population and bilateral in 45%-70% of cases n R  ib notching: coarctation of aorta most common and important cause; other causes: intercostal nerve tumors (neurilemoma, neurofibroma), subclavian artery obstruction, arteriovenous malformation involving intercostal artery and vein, and hyperparathyroidism

Suggested Readings Fefferman NR, Pinkney LP: Imaging evaluation of chest wall disorders in children. Radiol Clin North Am 43:355-370, 2005. Glass RB, Norton KI, Mitre SA, Kang E: Pediatric ribs: A spectrum of abnormalities. RadioGraphics 22:87-104, 2002. Goretsky MJ, Kelly RE Jr, Croitoru D, Nuss D: Chest wall anomalies: Pectus excavatum and pectus carinatum. Adolesc Med Clin 15:455471, 2004. Jeung MY, Gangi A, Gasser B, et al: Imaging of chest wall disorders. RadioGraphics 19:617-637, 1999. Kuhlman JE, Bouchardy L, Fishman EK, Zerhouni EA: CT and MR imaging evaluation of chest wall disorders. RadioGraphics 14:571595, 1994.

Tumors of Chest Wall DEFINITION: Metastases to the chest wall and direct extension by pulmonary carcinoma are common, but primary chest wall tumors are uncommon. IMAGING

DIAGNOSTIC PEARLS

Radiography

n M  ost

Findings n F  ibrous

dysplasia: osteolytic lesion with homogeneous “ground-glass” matrix and endosteal scalloping, with or without bone expansion n O  steochondroma: focal deformity or expansion of the rib with calcification of the cartilaginous cap n C  hondrosarcoma: large mineralized mass with characteristic rings and arches pattern of calcification, mainly arising from anterior rib or costochondral junction n O  steosarcoma: mixed sclerotic and lucent areas within the medullary cavity; cortical disruption, aggressive periosteal reaction; and associated soft tissue mass. n E  wing sarcoma/PNET: osteolytic lesions with cortical destruction, periosteal reaction, and associated soft tissue masses n M  ultiple myeloma: multifocal osteolytic lesions with a “motheaten” appearance n M  etastases: lytic destructive process in the medullary cavity with ill-defined margins, cortical erosion, and frequent soft tissue extension n I ntercostal nerve tumor: may result in rib erosion Utility

n U  sually

patients

first imaging modality performed in these

common chest wall bone tumors: metastases and multiple myeloma n M  ost common primary malignant chest wall bone tumor: chondrosarcoma n M  ost common benign rib lesion: fibrous dysplasia n M  ost common benign soft tissue tumor: lipoma n M  ost common soft tissue malignant tumor: malignant fibrous histiocytoma n I ntercostal

nerve sheath tumor (neurilemoma, neurofibroma): well-marginated, smooth mass along course of intercostal nerve; soft tissue or low attenuation with variable contrast enhancement n M  ultiple myeloma: multifocal osteolytic lesions with a “motheaten” appearance n M  etastases: lytic destructive process in the medullary cavity with ill-defined margins, cortical erosion, and frequent soft tissue extension Utility

n F  ibrous

dysplasia: CT enables more accurate assessment of lesion morphology, location, and extent over radiographs. n O  steochondroma: CT is particularly helpful if lesions are in the ribs, shoulder, or spine.

CT

MRI

n F  ibrous

n C  hondrosarcoma:

Findings

Findings

dysplasia: osteolytic lesion with homogeneous “ground-glass” matrix and endosteal scalloping, with or without bone expansion n O  steochondroma; focal expansion of the rib with calcification of the cartilaginous cap n C  hondrosarcoma: large mineralized mass with characteristic rings and arches pattern of calcification, mainly arising from anterior rib or costochondral junction; soft tissue component evident on CT n L  ipoma: mass with homogeneous density similar to subcutaneous fat n E  lastofibroma: lenticular, unencapsulated, soft tissue mass with skeletal muscle attenuation interspersed with strands of fat attenuation

destructive lesion with large soft tissue mass having characteristic peripheral and septal enhancement after contrast agent administration n E  wing sarcoma/PNET: large mixed-signal mass, disproportionately large compared with bone involvement n L  ipoma: mass with signal characteristics similar to subcutaneous fat n E  lastofibroma: lenticular, unencapsulated, soft tissue mass with skeletal muscle signal intensity interspersed with strands of fat signal intensity Utility

n F  ibrous

dysplasia: MRI enables more accurate assessment of lesion morphology, location, and extent over radiographs

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

n Benign



n Most



bone tumors of the chest wall are uncommon, the most common being osteochondroma. common chest wall benign soft tissue tumor is lipoma. n Most common primary malignant soft tissue tumor is malignant fibrous histiocytoma. n MRI is the best method to assess the extent of malignant chest wall tumors.

711

712    Tumors of Chest Wall

Figure 1.  Fibrous dysplasia in a 16-year-old girl with chest pain. Close-up view from chest radiograph shows an expanding, osteolytic lesion in the anterior aspect of the sixth rib (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Figure 3.  Osteochondroma of the rib in a 28-year-old man with an incidental finding on chest radiograph. CT scan at level of the costovertebral junction shows a mineralized mass arising from the rib (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

CHEST WALL

Figure 2.  Fibrous dysplasia in a 16-year-old girl with chest pain. CT scan shows a large lytic lesion in the rib. The lesion has caused cortical thinning and expansile remodeling of the rib (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Figure 4.  Chondrosarcoma of chest wall in a 45-year-old man with a painless, slowly growing mass in the lower chest wall. T2-weighted MR image shows a high signal intensity heterogenous mass, with lobulated appearance and low signal intensity septa between cartilaginous lobules (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

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CHEST WALL

n M  RI

is the best method to assess the extent of malignant chest wall tumors.

CLINICAL PRESENTATION n F  ibrous

dysplasia: virtually affects any bone and may be monostotic or polyostotic n M  ultiple myeloma: associated with presence of increased monoclonal immunoglobulin and light chain proteins in the blood and urine n M  etastases: pain, pathologic fractures, and hypercalcemia most common clinical manifestations n B  enign soft tissue tumors: typically manifest as painless, slow-growing, palpable masses n S  oft tissue sarcomas and primary malignant fibrous histiocytoma: manifest as painful and rapidly growing masses

DIFFERENTIAL DIAGNOSIS n M  etastases n M  ultiple

myeloma

n C  hondrosarcoma n O  steosarcoma n M  alignant n F  ibrous n L  ipoma

fibrous histiocytoma dysplasia

PATHOLOGY n C  hest

wall tumors are uncommon neoplasms that may arise from any of the chest wall tissues. n B  enign tumors are lipoma, osteochondroma, and fibrous dysplasia, whereas malignant tumor are chondrosarcoma, plasmacytoma, lymphoma, malignant fibrous histiocytoma, and osteosarcoma. n F  ibrous dysplasia is a skeletal developmental anomaly in which medullary bone is replaced by fibrous tissue with either monostotic or polyostotic involvement. n O  steochondroma is characterized by cartilage-capped bony growth that projects from affected bone surface. n L  ipomas are composed of mature fat cells and are usually encapsulated.

n O  steosarcoma

has malignant mesenchymal cells that produce osteoid or immature bone and has an aggressive pathologic behavior with mixed sclerosis/lucency within the medullary cavity. n I n children, primary malignancies are small round cell tumors, PNET, Askin tumors, rhabdomyosarcoma, and Ewing sarcoma.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ost

common benign rib lesion is fibrous dysplasia, followed by osteochondroma. n C  hondrosarcoma is most common adult malignant chest wall primary bone tumor, with 90% arising from the ribs. n E  wing sarcoma/PNET is most common primary chest wall tumor in children. n M  etastases are most common malignant tumors involving the skeleton; the osteolytic type is encountered most frequently, although sclerotic or mixed types occur. n V  ast majority of primary chest wall soft tissue tumors are benign, the most common one being lipoma. n E  lastofibroma is a relatively common fibroelastic pseudotumor that in almost 99% of the cases occurs in the subscapular region. n S  oft tissue sarcomas and primary malignant fibrous histiocytoma of the chest wall are rare.

Suggested Readings Jeung MY, Gangi A, Gasser B, et al: Imaging of chest wall disorders. RadioGraphics 19:617-637, 1999. O’Sullivan P, O’Dwyer H, Flint J, et al: Malignant chest wall neoplasms of bone and cartilage: A pictorial review of CT and MR findings. Br J Radiol 80:678-684, 2007. O’Sullivan P, O’Dwyer H, Flint J, et al: Soft tissue tumours and masslike lesions of the chest wall: A pictorial review of CT and MR findings. Br J Radiol 80:574-580, 2007. Tateishi U, Gladish GW, Kusumoto M, et al: Chest wall tumors: Radiologic findings and pathologic correlation: I. Benign tumors. RadioGraphics 23:1477-1490, 2003. Tateishi U, Gladish GW, Kusumoto M, et al: Chest wall tumors: Radiologic findings and pathologic correlation: II. Malignant tumors. RadioGraphics 23:1491-1508, 2003.

Infection of Chest Wall DEFINITION: A variety of inflammatory and infectious diseases may occur in the chest wall, ranging from inflammatory conditions of uncertain etiology to acute and chronic infections involving bone, joints, or soft tissues. IMAGING

DIAGNOSTIC PEARLS

Radiography

n S  ternal

Findings n S  oft

Utility n O  f

tissue swelling

limited value in the diagnosis

CT

Findings n S  oft

tissue swelling, abscess formation osteomyelitis: suspected when soft tissue abnormalities are associated with bone destruction, dehiscence, or severe demineralization n N  ecrotizing fasciitis: spontaneous necrosis and gas formation n A  ctinomycosis: lung infection may result in empyema and extend into chest wall n T  uberculosis: may result in chondritis, osteomyelitis, spondylitis, abscess formation, and empyema necessitatis n S  ternal

Utility n C  T

is used to assess extent and depth of infection and can be useful for surgical planning.

CLINICAL PRESENTATION n C  hest

pain, fever n N  ecrotizing fasciitis: high fever; red, painful swelling that spreads rapidly

DIFFERENTIAL DIAGNOSIS n P  ost-surgical

hematoma or seroma hematoma or seroma n C  hest wall abscess n S  ternal osteomyelitis n A  ctinomycosis n T  uberculosis n P  ost-traumatic

PATHOLOGY

osteomyelitis: soft tissue abnormalities associated with bone destruction, dehiscence, or severe demineralization n T  uberculosis: may result in chondritis, osteomyelitis, spondylitis, abscess formation, and empyema necessitatis n M  ajority of chest wall infections follow surgery (particularly median sternotomy) or trauma n S  oft

tissue infections may be classified into necrotizing fasciitis (subcutaneous fat and superficial fascia) and pyomyositis (muscles). n A  ctinomycosis is a chronic granulomatous infection characterized by suppuration, sulfur granules, abscess formation, and sinus tracts; pulmonary infection may progress to empyema and extend into chest wall. n T  uberculosis may result in chondritis, osteomyelitis, spondylitis, abscess formation, and empyema necessitatis. n E  mpyema necessitatis is leakage of empyema through parietal pleura with discharge of its contents into subcutaneous tissues of chest wall.

INCIDENCE/PREVALENCE AND EPIDEMIOLOGY n M  ajority

of chest wall infections follow surgery (particularly median sternotomy) or trauma. n O  ther causes include necrotizing fasciitis, intravenous drug use (abscess, osteomyelitis, diskitis), tuberculosis, and extension of intrathoracic infections (actinomycosis, tuberculosis, empyema necessitatis).

Suggested Readings Kwong JS, Müller NL, Godwin JD, et al: Thoracic actinomycosis: CT findings in eight patients. Radiology 183:189-192, 1992. Morris BS, Maheshwari M, Chalwa A: Chest wall tuberculosis: A review of CT appearances. Br J Radiol 77:449-457, 2004. Templeton PA, Fishman EK: CT evaluation of poststernotomy complications. AJR Am J Roentgenol 159:45-50, 1992.

n L  esions

range from inflammatory conditions of uncertain etiology to acute or chronic infections involving bone, joints, or soft tissues.

WHAT THE REFERRING PHYSICIAN NEEDS TO KNOW

714

n Contrast-enhanced

CT is the imaging modality of choice for the diagnosis of presence and extent of chest wall infection.

CHEST WALL

Figure 1.  Sternal dehiscence and infection from Staphylococcus aureus in a 65-year-old man after coronary artery bypass graft. CT scan photographed at bone window settings shows sternal dehiscence (arrows). Also noted are bilateral pleural effusions. (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Infection of Chest Wall    715

Figure 2.  Necrotizing fasciitis in a 66-year-old woman. CT image photographed at lung window settings shows large gas collections dissecting the fascial planes of the posterior upper chest wall (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)

Figure 3.  Necrotizing fasciitis in a 66-year-old woman. CT image photographed at soft window settings shows large gas collections dissecting the fascial planes of the posterior upper chest wall (arrows). (Courtesy of Dr. Tomás Franquet, Barcelona, Spain)